L. Bernal-González, H. J. Cabana-Méndez, G. A. Muñoz-Fernández and J. B. Seoane-Sepúlveda
Trans. Amer. Math. Soc. 373 (2020), 3063-3083.
Abstract, references and article information

Banks and financial institutions taking part in providing mortgage loans for the Housing Authority Subsidised Sale Flats Scheme (SSFS) may offer a mortgage principal moratorium plan to the scheme’s mortgagors.

The authority today wrote to these institutions to confirm and agree that such a plan is applicable for SSFS flats.

Principal repayment may be deferred for a maximum 12-month period and the mortgage loan repayment period may be extended correspondingly by a maximum of 12 months.

The principal moratorium period may commence by December 31 this year at the latest.

The arrangement is applicable to the Home Ownership Scheme, the Private Sector Participation Scheme, the Buy or Rent Option Scheme, the Tenants Purchase Scheme and the Green Form Subsidised Home Ownership Scheme in the primary market and under the Secondary Market Scheme.

To encourage participating financial institutions to provide mortgage loans and better mortgage terms for SSFS flat purchasers, the authority provides a mortgage default guarantee for them.

It undertakes to meet the shortfall in repayment in the event of default by the borrowers under specified circumstances during the guarantee period.

Due to the requirements in the guarantee deed on the mortgage loan period and the monthly instalment amount, participating financial institutions may not be able to offer a mortgage principal moratorium plan to SSFS flat owners.

In light of the economic downturn arising from the COVID-19 outbreak, the authority confirmed today that a mortgage principal moratorium plan is applicable for SSFS flats.

The move will encourage participating financial institutions to offer such a plan to SSFS flat owners, reducing their burden of mortgage repayment.

Applications for the $1.3 billion in subsidies earmarked for registered owners of goods vehicles and green minibus operators under the Anti-epidemic Fund opened today, the Transport Department announced.

A one-off non-accountable subsidy of $10,000 will be provided to each registered goods vehicle owner for each goods vehicle.

From today until September 30, registered owners of goods vehicles who have received the department's letters must use the registration PIN provided in the letters for submission of registrations through GovHK.

After successful completion of registration, the subsidy will be disbursed to the designated local bank account provided in the registration through autopay in about two to three weeks.

Cross-boundary goods vehicle drivers who conduct nucleic acid tests in Hong Kong can apply for the subsidy on an accountable basis, with the maximum amount being $350 per test.

A one-off non-accountable subsidy of $30,000 per green minibus will be provided to each holder of a Passenger Service Licence-Public Light Bus (Scheduled) Service who has been approved to operate a relevant green minibus route package.

The department briefed the green minibus trade today on the subsidy arrangement and application details with the distribution of the application forms.

Green minibus operators are required to send the completed application forms to the department by post on or before September 30.

After the department has verified their submissions, the subsidy will be disbursed through autopay in about one month.

To assist the transport trades to cope with operational demands in the prevailing economic environment, the Government has rolled out the fuel subsidy and one-off subsidy measures under the first round of the Anti-epidemic Fund progressively.

As of mid-April, the department has received applications for subsidies from three franchised bus companies, 10 franchised and licensed ferry operators, Hong Kong Tramways Limited, registrations from 1,700 registered owners of non-franchised public buses, school private light buses and hire cars. Over $100 million of the subsidies have been disbursed.

Click here for details.

Property management companies and owners’ organisations which have successfully applied for an anti-epidemic support scheme were reminded today to disburse the hardship allowance to frontline workers as soon as practicable upon receiving the subsidies.

The Home Affairs Department said the workers concerned shall acknowledge receipt of the allowance using the prescribed forms.

The property management companies or owners’ organisations shall submit a report on the allowance’s overall payment to the Property Management Services Authority within three months of receiving the subsidies.

The department and/or the authority will conduct a random review and check to ensure that the frontline property management workers have received the allowance.

As of today, more than 8,160 applications have been received for the Anti-epidemic Support Scheme for Property Management Sector under the Anti-epidemic Fund.

About 2,850 applications have been approved, involving more than $100 million in subsidies and benefitting more than 17,500 building blocks and about 25,500 frontline workers.

Call 3696 1156 or 3696 1166 for enquiries.

The Commerce & Economic Development Bureau today announced that the subsidy quota for three mask production lines have been reassigned.

Three production lines, previously approved under the Local Mask Production Subsidy Scheme, have withdrawn from the scheme, the Government said.

The subsidy quota concerned has been allocated to SDL Skin (Asia), Safeguard HK and SwissTech.

SDL Skin (Asia) has been approved for obtaining a subsidy for a second production line and is expected to supply an average of 1.6 million masks every month to the Government. The production line may receive a subsidy of up to $1 million.

Safeguard HK has been approved for obtaining a subsidy for one production line and is expected to supply an average of 500,000 masks to the Government every month. The production line may receive up to $2 million.

SwissTech has been approved for obtaining a subsidy for one production line and is expected to supply an average of 2 million masks every month to the Government and produce a further 1 million masks on average monthly for the local market.

The production line may receive up to $3 million.

It is estimated that when all 20 subsidised lines under the scheme are in full production, they will collectively supply 33.85 million masks to the Government and a further 7.15 million to the local market monthly.

The companies which withdrew from the scheme were CareHK and Shang Manufactory.

The Government did not sign agreements with or make disbursements to these firms.

The Food & Environmental Hygiene Department announced that applications for the Catering Business (Social Distancing) Subsidy Scheme, under the second round of the Anti-epidemic Fund, will start from May 5.

The department said the scheme, which is estimated to benefit 16,000 catering outlets and their employees, will provide financial relief measures to the catering businesses which have been hard hit by the COVID-19 epidemic and social distancing measures.

It will provide subsidies ranging from $250,000 to $2,200,000 to eligible licence holders of general restaurants, light refreshment restaurants, marine restaurants and factory canteens in operation according to the floor area of the premises as specified on the licence.

The primary goal of the scheme is to support the payment of employees' salaries during a six-month period following application approval.

To provide immediate relief to the catering sector, the subsidy will be dished out upfront, in two tranches.

To avoid abuse, applicants should undertake that there will be no redundancy of staff for three months on receipt of the first tranche of subsidy and another three months on receipt of the second tranche.

They should also undertake that not less than 80% of the subsidies for respective months would be used to pay salaries of staff working at the premises.

Applicants should submit within a specified period a certificate issued by a Certified Public Accountant (practising) on its total staff salaries and total number of salaried staff for each of the months covered by the subsidy.

They should also submit a certificate issued by a CPA on its total staff salaries and total number of staff working at the premises for the month of March this year.

To avoid double benefits, applicants should declare that they have not and will not submit any application under the Employment Support Scheme.

Each catering outlet directed to close its licensed premises under the Prevention & Control of Disease (Requirements & Directions) (Business & Premises) Regulation, including karaoke establishments, nightclubs and bars or pubs, is eligible for a further one-off subsidy of $50,000.

Applications should be submitted to the department's District Environmental Hygiene Offices in person or by mail. Food licence holders can also submit their applications through the website.

The deadline for application is June 5.

Upon receipt of the completed application form and supporting documents and after verification, the disbursement of the first tranche of subsidies can generally be made in two to three weeks by crossed cheques to the corresponding licensed food premises.

Aldehyde oxidases (AOXs) are a small group of enzymes belonging to the larger family of molybdo-flavoenzymes, along with the well-characterized xanthine oxidoreductase. The two major types of reactions that are catalyzed by AOXs are the hydroxylation of heterocycles and the oxidation of aldehydes to their corresponding carboxylic acids. Different animal species have different complements of AOX genes. The two extremes are represented in humans and rodents; whereas the human genome contains a single active gene (AOX1), those of rodents, such as mice, are endowed with four genes (Aox1-4), clustering on the same chromosome, each encoding a functionally distinct AOX enzyme. It still remains enigmatic why some species have numerous AOX enzymes, whereas others harbor only one functional enzyme. At present, little is known about the physiological relevance of AOX enzymes in humans and their additional forms in other mammals. These enzymes are expressed in the liver and play an important role in the metabolisms of drugs and other xenobiotics. In this review, we discuss the expression, tissue-specific roles, and substrate specificities of the different mammalian AOX enzymes and highlight insights into their physiological roles.

Sulfur is essential for biological processes such as amino acid biogenesis, iron–sulfur cluster formation, and redox homeostasis. To acquire sulfur-containing compounds from the environment, bacteria have evolved high-affinity uptake systems, predominant among which is the ABC transporter family. Theses membrane-embedded enzymes use the energy of ATP hydrolysis for transmembrane transport of a wide range of biomolecules against concentration gradients. Three distinct bacterial ABC import systems of sulfur-containing compounds have been identified, but the molecular details of their transport mechanism remain poorly characterized. Here we provide results from a biochemical analysis of the purified Escherichia coli YecSC-FliY cysteine/cystine import system. We found that the substrate-binding protein FliY binds l-cystine, l-cysteine, and d-cysteine with micromolar affinities. However, binding of the l- and d-enantiomers induced different conformational changes of FliY, where the l- enantiomer–substrate-binding protein complex interacted more efficiently with the YecSC transporter. YecSC had low basal ATPase activity that was moderately stimulated by apo FliY, more strongly by d-cysteine–bound FliY, and maximally by l-cysteine– or l-cystine–bound FliY. However, at high FliY concentrations, YecSC reached maximal ATPase rates independent of the presence or nature of the substrate. These results suggest that FliY exists in a conformational equilibrium between an open, unliganded form that does not bind to the YecSC transporter and closed, unliganded and closed, liganded forms that bind this transporter with variable affinities but equally stimulate its ATPase activity. These findings differ from previous observations for similar ABC transporters, highlighting the extent of mechanistic diversity in this large protein family.

The protein-tyrosine phosphatase SHP2 is an allosteric enzyme critical for cellular events downstream of growth factor receptors. Mutations in the SHP2 gene have been linked to many different types of human diseases, including developmental disorders, leukemia, and solid tumors. Unlike most SHP2-activating mutations, the T507K substitution in SHP2 is unique in that it exhibits oncogenic Ras-like transforming activity. However, the biochemical basis of how the SHP2/T507K variant elicits transformation remains unclear. By combining kinetic and biophysical methods, X-ray crystallography, and molecular modeling, as well as using cell biology approaches, here we uncovered that the T507K substitution alters both SHP2 substrate specificity and its allosteric regulatory mechanism. We found that although SHP2/T507K exists in the closed, autoinhibited conformation similar to the WT enzyme, the interactions between its N-SH2 and protein-tyrosine phosphatase domains are weakened such that SHP2/T507K possesses a higher affinity for the scaffolding protein Grb2-associated binding protein 1 (Gab1). We also discovered that the T507K substitution alters the structure of the SHP2 active site, resulting in a change in SHP2 substrate preference for Sprouty1, a known negative regulator of Ras signaling and a potential tumor suppressor. Our results suggest that SHP2/T507K's shift in substrate specificity coupled with its preferential association of SHP2/T507K with Gab1 enable the mutant SHP2 to more efficiently dephosphorylate Sprouty1 at pTyr-53. This dephosphorylation hyperactivates Ras signaling, which is likely responsible for SHP2/T507K's Ras-like transforming activity.

Bacterial type VII secretion systems secrete a wide range of extracellular proteins that play important roles in bacterial viability and in interactions of pathogenic mycobacteria with their hosts. Mycobacterial type VII secretion systems consist of five subtypes, ESX-1–5, and have four substrate classes, namely, Esx, PE, PPE, and Esp proteins. At least some of these substrates are secreted as heterodimers. Each ESX system mediates the secretion of a specific set of Esx, PE, and PPE proteins, raising the question of how these substrates are recognized in a system-specific fashion. For the PE/PPE heterodimers, it has been shown that they interact with their cognate EspG chaperone and that this chaperone determines the designated secretion pathway. However, both structural and pulldown analyses have suggested that EspG cannot interact with the Esx proteins. Therefore, the determining factor for system specificity of the Esx proteins remains unknown. Here, we investigated the secretion specificity of the ESX-1 substrate pair EsxB_1/EsxA_1 in Mycobacterium marinum. Although this substrate pair was hardly secreted when homologously expressed, it was secreted when co-expressed together with the PE35/PPE68_1 pair, indicating that this pair could stimulate secretion of the EsxB_1/EsxA_1 pair. Surprisingly, co-expression of EsxB_1/EsxA_1 with a modified PE35/PPE68_1 version that carried the EspG5 chaperone-binding domain, previously shown to redirect this substrate pair to the ESX-5 system, also resulted in redirection and co-secretion of the Esx pair via ESX-5. Our results suggest a secretion model in which PE35/PPE68_1 determines the system-specific secretion of EsxB_1/EsxA_1.

The Government today said the first batch of subsidies amounting to $5.6 million under two relief measures for recyclers has been disbursed, while $5.6 million in subsidies had been approved under a management sector support scheme.

The two Recycling Fund measures aim to help the recycling industry cope with the current economic situation and recent operational difficulties arising from the COVID-19 epidemic.

The Advisory Committee on Recycling Fund announced in mid-March to reserve $100 million to launch the One-off Recycling Industry Anti-epidemic Scheme.

The scheme provides timely financial support to help with recyclers’ operational costs for six months. The funding limit for each recycler is $20,000 per month from January 1 to June 30, or $120,000 in total maximum subsidy.

The committee has also allocated additional funds to extend the earlier-launched One-off Rental Support Scheme for another six months, providing a total funding of $200 million to fight the virus and help the recycling industry ride out the difficult times.

The rental support scheme, which benefits street-corner recycling shops and recycling sites, originally ran from October to March. It has been extended for six months until September this year, totalling 12 months.

The monthly rental subsidy for each recycler is capped at $25,000, setting the maximum total rental subsidy at $300,000.

Separately, the Anti-epidemic Support Scheme for Property Management Sector has approved 205 applications involving around $5.6 million in subsidies to benefit more than 1,500 building blocks.

The relevant property management companies and owners’ organisations will receive notifications for subsidy disbursement shortly.

The list of properties for which applications have been approved is available online.

Briefing sessions were held earlier to introduce the scheme to the property management sector and owners’ organisations.

The Government today announced that the Environment Bureau has disbursed about $6.5 million in subsidies to 809 private municipal solid waste collectors by cheque.

Under the Government's latest round of anti-epidemic measures, the bureau launched the Subsidy Scheme for the Refuse Transfer Station Account Holders for Transporting Municipal Solid Waste to provide a one-off relief subsidy of $8,000 to each eligible private municipal solid waste collector.

To provide financial support to the industry as soon as possible, the Environmental Protection Department, following funding approval by the Legislative Council Finance Committee, expedited the subsidy disbursement arrangement by waiving the application procedures.

The cheques have been issued and posted to all eligible private collectors.

Eligible collectors are refuse transfer station account holders who transported municipal solid waste to refuse transfer stations or landfills in the first quarter of the year.

The subsidy will assist them in increasing resources to enhance workers' personal protective equipment and strengthen the disinfection of refuse transport vehicles to curb the risk of virus transmission and maintain environmental hygiene.

It is possible that the next time you walk into a bar you may find that there is only standing room, and you are among a handful of persons allowed inside. Prime Minister Andrew Holness said that in addition to having a specific gathering rule,...

Eva Griesser
May 1, 2020; 19:839-851
Research

Purpose: To investigate differences between positron emission tomography/magnetic resonance imaging (PET/MRI) and PET/computed tomography (PET/CT) in lesion detection and classification in oncological whole-body examinations and to investigate radiation exposure differences between both modalities. Material and Methods: In this prospective, single-center, observational study 1003 oncological examinations (918 patients, mean age 57.8±14.4y) were included. Patients underwent PET/CT and subsequent PET/MRI (149.8±49.7min after tracer administration). Examinations were reviewed by radiologists and nuclear medicine physicians in consensus. Additional findings, characterization of indetermiante findings in PETCT, missed findings in PET/MRI including their clinical relevance and effective dose of both modalities were investigated. McNemar’s test was used to compare lesion detection between both hybrid imaging modalities (p<0.001 indicating statistical significance). Results: Additional information in PET/MRI was reported in 26.3% (264/1003) of examinations compared to PET/CT (p<0.001). Of these, additional malignant findings were detected in 5.3% (53/1003), leading to a change in TNM-staging in 2.9% (29/1003) due to PET/MRI. Definite lesion classification of indeterminate PET/CT findings was possible in 11.1% (111/1003) with PET/MRI. In 2.9% (29/1003), lesions detected in PET/CT were not visible in PET/MRI. Malignant lesions were missed in 1.2% (12/1003) by PET/MRI leading to a change in TNM-staging in 0.5% (5/1003). The estimated mean effective-dose for whole-body PET/CT amounted to 17.6±8.7mSv in comparison to 3.6±1.4mSv in PET/MRI, resulting in a potential dose reduction of 79.6% (p<0.001). Conclusion: PET/MRI improves lesion detection and potentially reduces additional examinations in tumor staging. Especially younger patients may benefit from the clinically relevant dose reduction of PET/MRI compared to PET/CT.

Mycobacterial Ser/Thr protein kinases (STPKs) play a critical role in signal transduction pathways that ultimately determine mycobacterial growth and metabolic adaptation. Identification of key physiological substrates of these protein kinases is, therefore, crucial to better understand how Ser/Thr phosphorylation contributes to mycobacterial environmental adaptation, including response to stress, cell division, and host-pathogen interactions. Various substrate detection methods have been employed with limited success, with direct targets of STPKs remaining elusive. Recently developed mass spectrometry (MS)-based phosphoproteomic approaches have expanded the list of potential STPK substrate identifications, yet further investigation is required to define the most functionally significant phosphosites and their physiological importance. Prior to the application of MS workflows, for instance, GarA was the only known and validated physiological substrate for protein kinase G (PknG) from pathogenic mycobacteria. A subsequent list of at least 28 candidate PknG substrates has since been reported with the use of MS-based analyses. Herein, we integrate and critically review MS-generated datasets available on novel STPK substrates and report new functional and subcellular localization enrichment analyses on novel candidate protein kinase A (PknA), protein kinase B (PknB) and PknG substrates to deduce the possible physiological roles of these kinases. In addition, we assess substrate specificity patterns across different mycobacterial STPKs by analyzing reported sets of phosphopeptides, in order to determine whether novel motifs or consensus regions exist for mycobacterial Ser/Thr phosphorylation sites. This review focuses on MS-based techniques employed for STPK substrate identification in mycobacteria, while highlighting the advantages and challenges of the various applications.

Laser-capture microdissection (LCM) allows the visualization and isolation of morphologically distinct subpopulations of cells from heterogeneous tissue specimens. In combination with formalin-fixed and paraffin-embedded (FFPE) tissue it provides a powerful tool for retrospective and clinically relevant studies of tissue proteins in a healthy and diseased context. We first optimized the protocol for efficient LCM analysis of FFPE tissue specimens. The use of SDS containing extraction buffer in combination with the single-pot solid-phase-enhanced sample preparation (SP3) digest method gave the best results regarding protein yield and protein/peptide identifications. Microdissected FFPE human substantia nigra tissue samples (~3,000 cells) were then analyzed, using tandem mass tag (TMT) labeling and LC-MS/MS, resulting in the quantification of >5,600 protein groups. Nigral proteins were classified and analyzed by abundance, showing an enrichment of extracellular exosome and neuron-specific gene ontology (GO) terms among the higher abundance proteins. Comparison of microdissected samples with intact tissue sections, using a label-free shotgun approach, revealed an enrichment of neuronal cell type markers, such as tyrosine hydroxylase and alpha-synuclein, as well as proteins annotated with neuron-specific GO terms. Overall, this study provides a detailed protocol for laser-capture proteomics using FFPE tissue and demonstrates the efficiency of LCM analysis of distinct cell subpopulations for proteomic analysis using low sample amounts.

Keisuke Mori
Apr 29, 2020; 0:jlr.RA120000803v1-jlr.RA120000803
Research Articles

A classic edition of the pod as we hark back to the hallowed three topic format. Henry Burrell hosts David Price, Scott Carey and Chris Martin to ask just how Netflix got so popular. Will it sustain it though? Windows Phone is also pretty much actually dead but the funeral march is long. Other phone stuff includes the hallowed iPhone 8, the demise of Vertu and Nokia not really being Nokia. David then tells us why Google Glass is back, what it means for the enterprise, and why didn't they realise the first time round that it wasn't a consumer play?  

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The yeast protein Mpo1 belongs to a protein family that is widely conserved in bacteria, fungi, protozoa, and plants, and is the only protein of this family whose function has so far been elucidated. Mpo1 is an Fe²⁺-dependent dioxygenase that catalyzes the α-oxidation reaction of 2-hydroxy (2-OH) long-chain FAs produced in the degradation pathway of the long-chain base phytosphingosine. However, several biochemical characteristics of Mpo1, such as its catalytic residues, membrane topology, and substrate specificity, remain unclear. Here, we report that yeast Mpo1 contains two transmembrane domains and that both its N- and C-terminal regions are exposed to the cytosol. Mutational analyses revealed that three histidine residues conserved in the Mpo1 family are especially important for Mpo1 activity, suggesting that they may be responsible for the formation of coordinate bonds with Fe²⁺. We found that, in addition to activity toward 2-OH long-chain FAs, Mpo1 also exhibits activity toward 2-OH very-long-chain FAs derived from the FA moiety of sphingolipids. These results indicate that Mpo1 is involved in the metabolism of long-chain to very-long-chain 2-OH FAs produced in different pathways. We noted that the growth of mpo1 cells is delayed upon carbon deprivation, suggesting that the Mpo1-mediated conversion of 2-OH FAs to non-hydroxy FAs is important for utilizing 2-OH FAs as a carbon source under carbon starvation. Our findings help to elucidate the as-yet-unknown functions and activities of other Mpo1 family members.

Whether HDL is associated with dementia risk is unclear. In addition to apoA1, other apolipoproteins are found in HDL, creating subspecies of HDL that may have distinct metabolic properties. We measured apoA1, apoC3, and apoJ levels in plasma and apoA1 levels in HDL that contains or lacks apoE, apoJ, or apoC3 using a modified sandwich ELISA in a case-cohort study nested within the Ginkgo Evaluation of Memory Study. We included 995 randomly selected participants and 521 participants who developed dementia during a mean of 5.1 years of follow-up. The level of total apoA1 was not significantly related to dementia risk, regardless of the coexistence of apoC3, apoJ, or apoE. Higher levels of total plasma apoC3 were associated with better cognitive function at baseline (difference in Modified Mini-Mental State Examination scores tertile 3 vs. tertile 1: 0.60; 95% CI: 0.23, 0.98) and a lower dementia risk (adjusted hazard ratio tertile 3 vs. tertile 1: 0.73; 95% CI: 0.55, 0.96). Plasma concentrations of apoA1 in HDL and its apolipoprotein-defined subspecies were not associated with cognitive function at baseline or with the risk of dementia during follow-up. Similar studies in other populations are required to better understand the association between apoC3 and Alzheimer’s disease pathology.

Cholesterol/sphingolipid-rich membrane domains, known as lipid rafts or membrane rafts, play a critical role in the compartmentalization of signaling pathways. Physical segregation of proteins in lipid rafts may modulate the accessibility of proteins to regulatory or effector molecules. Thus, lipid rafts serve as sorting platforms and hubs for signal transduction proteins. Cancer cells contain higher levels of intracellular cholesterol and lipid rafts than their normal non-tumorigenic counterparts. Many signal transduction processes involved in cancer development (insulin-like growth factor system and phosphatidylinositol 3-kinase-AKT) and metastasis [cluster of differentiation (CD)44] are dependent on or modulated by lipid rafts. Additional proteins playing an important role in several malignant cancers (e.g., transmembrane glycoprotein mucin 1) are also being detected in association with lipid rafts, suggesting a major role of lipid rafts in tumor progression. Conversely, lipid rafts also serve as scaffolds for the recruitment and clustering of Fas/CD95 death receptors and downstream signaling molecules leading to cell death-promoting raft platforms. The partition of death receptors and downstream signaling molecules in aggregated lipid rafts has led to the formation of the so-called cluster of apoptotic signaling molecule-enriched rafts, or CASMER, which leads to apoptosis amplification and can be pharmacologically modulated. These death-promoting rafts can be viewed as a linchpin from which apoptotic signals are launched. In this review, we discuss the involvement of lipid rafts in major signaling processes in cancer cells, including cell survival, cell death, and metastasis, and we consider the potential of lipid raft modulation as a promising target in cancer therapy.

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Sulfur is essential for biological processes such as amino acid biogenesis, iron–sulfur cluster formation, and redox homeostasis. To acquire sulfur-containing compounds from the environment, bacteria have evolved high-affinity uptake systems, predominant among which is the ABC transporter family. Theses membrane-embedded enzymes use the energy of ATP hydrolysis for transmembrane transport of a wide range of biomolecules against concentration gradients. Three distinct bacterial ABC import systems of sulfur-containing compounds have been identified, but the molecular details of their transport mechanism remain poorly characterized. Here we provide results from a biochemical analysis of the purified Escherichia coli YecSC-FliY cysteine/cystine import system. We found that the substrate-binding protein FliY binds l-cystine, l-cysteine, and d-cysteine with micromolar affinities. However, binding of the l- and d-enantiomers induced different conformational changes of FliY, where the l- enantiomer–substrate-binding protein complex interacted more efficiently with the YecSC transporter. YecSC had low basal ATPase activity that was moderately stimulated by apo FliY, more strongly by d-cysteine–bound FliY, and maximally by l-cysteine– or l-cystine–bound FliY. However, at high FliY concentrations, YecSC reached maximal ATPase rates independent of the presence or nature of the substrate. These results suggest that FliY exists in a conformational equilibrium between an open, unliganded form that does not bind to the YecSC transporter and closed, unliganded and closed, liganded forms that bind this transporter with variable affinities but equally stimulate its ATPase activity. These findings differ from previous observations for similar ABC transporters, highlighting the extent of mechanistic diversity in this large protein family.

Fucosylation of the innermost GlcNAc of N-glycans by fucosyltransferase 8 (FUT8) is an important step in the maturation of complex and hybrid N-glycans. This simple modification can dramatically affect the activities and half-lives of glycoproteins, effects that are relevant to understanding the invasiveness of some cancers, development of mAb therapeutics, and the etiology of a congenital glycosylation disorder. The acceptor substrate preferences of FUT8 are well-characterized and provide a framework for understanding N-glycan maturation in the Golgi; however, the structural basis of these substrate preferences and the mechanism through which catalysis is achieved remain unknown. Here we describe several structures of mouse and human FUT8 in the apo state and in complex with GDP, a mimic of the donor substrate, and with a glycopeptide acceptor substrate at 1.80–2.50 Å resolution. These structures provide insights into a unique conformational change associated with donor substrate binding, common strategies employed by fucosyltransferases to coordinate GDP, features that define acceptor substrate preferences, and a likely mechanism for enzyme catalysis. Together with molecular dynamics simulations, the structures also revealed how FUT8 dimerization plays an important role in defining the acceptor substrate-binding site. Collectively, this information significantly builds on our understanding of the core fucosylation process.

Marlou L. Dirks
Oct 1, 2016; 65:2862-2875
Metabolism

AS ARTISTES and musicians try to manage the situation brought on by COVID-19’s stranglehold on the world and its economy, in the interim, many have resorted to hosting live-stream events. But that only succeeds to a point. Performers retain their...

Western Bureau: A number of swimming officials in western Jamaica say that the region’s struggles with underdevelopment will continue even if the COVID-19 pandemic is brought under control. They say this is because they still lack proper pools to...

Invitation Only Research Event

OBJECTIVE

Dysglycemia, in this survey defined as impaired glucose tolerance (IGT) or type 2 diabetes, is common in patients with coronary artery disease (CAD) and associated with an unfavorable prognosis. This European survey investigated dysglycemia screening and risk factor management of patients with CAD in relation to standards of European guidelines for cardiovascular subjects.

OBJECTIVE

To assess the contemporaneous prevalence of diabetic peripheral neuropathy (DPN) in people with type 1 diabetes (T1D) in Scotland and study its cross-sectional association with risk factors and other diabetic complications.

Ele Ferrannini
Jul 1, 2016; 39:1108-1114
Diabetes Care Symposium

Just days after South Korea loosened its social distancing guidelines, a new COVID-19 cluster of infections has sprung up in the capital city of Seoul tied to several nightclubs.

The Duluth Dental Forum in northeastern Minnesota celebrated its 75th anniversary in late 2019, stating that it was the second-oldest study club of its kind in the United States.