3-Mercaptopyruvate sulfur transferase (MPST) catalyzes the desulfuration of 3-mercaptopyruvate (3-MP) and transfers sulfane sulfur from an enzyme-bound persulfide intermediate to thiophilic acceptors such as thioredoxin and cysteine. Hydrogen sulfide (H2S), a signaling molecule implicated in many physiological processes, can be released from the persulfide product of the MPST reaction. Two splice variants of MPST, differing by 20 amino acids at the N terminus, give rise to the cytosolic MPST1 and mitochondrial MPST2 isoforms. Here, we characterized the poorly-studied MPST1 variant and demonstrated that substitutions in its Ser–His–Asp triad, proposed to serve a general acid–base role, minimally affect catalytic activity. We estimated the 3-MP concentration in murine liver, kidney, and brain tissues, finding that it ranges from 0.4 μmol·kg−1 in brain to 1.4 μmol·kg−1 in kidney. We also show that N-acetylcysteine, a widely-used antioxidant, is a poor substrate for MPST and is unlikely to function as a thiophilic acceptor. Thioredoxin exhibits substrate inhibition, increasing the KM for 3-MP ∼15-fold compared with other sulfur acceptors. Kinetic simulations at physiologically-relevant substrate concentrations predicted that the proportion of sulfur transfer to thioredoxin increases ∼3.5-fold as its concentration decreases from 10 to 1 μm, whereas the total MPST reaction rate increases ∼7-fold. The simulations also predicted that cysteine is a quantitatively-significant sulfane sulfur acceptor, revealing MPST's potential to generate low-molecular-weight persulfides. We conclude that the MPST1 and MPST2 isoforms are kinetically indistinguishable and that thioredoxin modulates the MPST-catalyzed reaction in a physiologically-relevant concentration range.

Covalent chemical modifications of cellular RNAs directly impact all biological processes. However, our mechanistic understanding of the enzymes catalyzing these modifications, their substrates and biological functions, remains vague. Amongst RNA modifications N⁶-methyladenosine (m⁶A) is widespread and found in messenger (mRNA), ribosomal (rRNA), and noncoding RNAs. Here, we undertook a systematic screen to uncover new RNA methyltransferases. We demonstrate that the methyltransferase-like 5 (METTL5) protein catalyzes m⁶A in 18S rRNA at position A₁₈₃₂. We report that absence of Mettl5 in mouse embryonic stem cells (mESCs) results in a decrease in global translation rate, spontaneous loss of pluripotency, and compromised differentiation potential. METTL5-deficient mice are born at non-Mendelian rates and develop morphological and behavioral abnormalities. Importantly, mice lacking METTL5 recapitulate symptoms of patients with DNA variants in METTL5, thereby providing a new mouse disease model. Overall, our biochemical, molecular, and in vivo characterization highlights the importance of m⁶A in rRNA in stemness, differentiation, development, and diseases.

Acetylation is a conserved modification used to regulate a variety of cellular pathways, such as gene expression, protein synthesis, detoxification, and virulence. Acetyltransferase enzymes transfer an acetyl moiety, usually from acetyl coenzyme A (AcCoA), onto a target substrate, thereby modulating activity or stability. Members of the GCN5-N-acetyltransferase (GNAT) protein superfamily are found in all domains of life and are characterized by a core structural domain architecture. These enzymes can modify primary amines of small molecules or of lysyl residues of proteins. From the initial discovery of antibiotic acetylation, GNATs have been shown to modify a myriad of small-molecule substrates, including tRNAs, polyamines, cell wall components, and other toxins. This review focuses on the literature on small-molecule substrates of GNATs in bacteria, including structural examples, to understand ligand binding and catalysis. Understanding the plethora and versatility of substrates helps frame the role of acetylation within the larger context of bacterial cellular physiology.

Vibralactone, a hybrid compound derived from phenols and a prenyl group, is a strong pancreatic lipase inhibitor with a rare fused bicyclic β-lactone skeleton. Recently, a researcher reported a vibralactone derivative (compound C1) that caused inhibition of pancreatic lipase with a half-maximal inhibitory concentration of 14 nM determined by structure-based optimization, suggesting a potential candidate as a new antiobesity treatment. In the present study, we sought to identify the main gene encoding prenyltransferase in Stereum vibrans, which is responsible for the prenylation of phenol leading to vibralactone synthesis. Two RNA silencing transformants of the identified gene (vib-PT) were obtained through Agrobacterium tumefaciens-mediated transformation. Compared to wild-type strains, the transformants showed a decrease in vib-PT expression ranging from 11.0 to 56.0% at 5, 10, and 15 days in reverse transcription-quantitative PCR analysis, along with a reduction in primary vibralactone production of 37 to 64% at 15 and 21 days, respectively, as determined using ultra-high-performance liquid chromatography-mass spectrometry analysis. A soluble and enzymatically active fusion Vib-PT protein was obtained by expressing vib-PT in Escherichia coli, and the enzyme’s optimal reaction conditions and catalytic efficiency (K_m/k_cat) were determined. In vitro experiments established that Vib-PT catalyzed the C-prenylation at C-3 of 4-hydroxy-benzaldehyde and the O-prenylation at the 4-hydroxy of 4-hydroxy-benzenemethanol in the presence of dimethylallyl diphosphate. Moreover, Vib-PT shows promiscuity toward aromatic compounds and prenyl donors.

IMPORTANCE Vibralactone is a lead compound with a novel skeleton structure that shows strong inhibitory activity against pancreatic lipase. Vibralactone is not encoded by the genome directly but rather is synthesized from phenol, followed by prenylation and other enzyme reactions. Here, we used an RNA silencing approach to identify and characterize a prenyltransferase in a basidiomycete species that is responsible for the synthesis of vibralactone. The identified gene, vib-PT, was expressed in Escherichia coli to obtain a soluble and enzymatically active fusion Vib-PT protein. In vitro characterization of the enzyme demonstrated the catalytic mechanism of prenylation and broad substrate range for different aromatic acceptors and prenyl donors. These characteristics highlight the possibility of Vib-PT to generate prenylated derivatives of aromatics and other compounds as improved bioactive agents or potential prodrugs.

Anything that encourages more people to enable two-step verification can only be a good thing.

Chelsea news and gossip is coming in thick and fast so Express Sport is on hand to bring you all the very latest from Stamford Bridge.

Liverpool are looking to make Sadio Mane an offer that would tarnish Real Madrid's hopes of signing him.

The summer transfer window is nearly upon us as Manchester United, Chelsea, Liverpool, Arsenal and the rest of the Premier League look to strengthen for whenever the new season starts. Express Sport brings you the latest updates throughout the day.

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The Real Madrid midfielder got creative as he denied a report claiming that he would be included in a swap deal that would see him join Sevilla

Damien Comolli, who took the England international to Anfield, saw the Reds enter into transfer talks with the Cottagers during the summer of 2012

One Arsenal star is on the list of the top ten Premier League players for increased transfer value in 2019.

Researchers have used a microbiome 'fingerprint' method to report that an individualized mosaic of microbial strains is transmitted to the infant gut microbiome from a mother giving birth through vaginal delivery. They detailed this transmission by analyzing existing metagenomic databases of fecal samples from mother-infant pairs, as well as analyzing mouse dam and pup transmission in a germ-free, or gnotobiotic, mouse model, where the dams were inoculated with human fecal microbes.

An infamous sex predator dubbed "the Notting Hill rapist" has been recommended for transfer to an open prison.

Barcelona forward Lionel Messi has taken to Instagram to dismiss a report claiming he will sign for Inter Milan in the summer... and that he paid bail money to get former teammate Ronaldinho out of prison.

Juan Mata believes Jadon Sancho is a "great player" as Manchester United continue to be linked with the winger.

Welcome to the Evening Standard's live blog covering the latest transfer news and rumours from the Premier League and beyond.

Arsenal and Manchester United have been linked with a move for Bayern Munich star Corentin Tolisso, but it is the Gunners who may have the transfer edge.

Marcus Rashford has been leading Manchester United's charm offensive to bring Jadon Sancho to Old Trafford - and he will have another chance tonight.

RB Leipzig chief executive Oliver Mintzlaff insists he is calm over the future of Timo Werner amid speculation linking the forward with Liverpool and Chelsea.

Manchester United are yet to offer Odion Ighalo a permanent deal with Ole Gunnar Solskjaer undecided over his plans to sign a striker this summer.

Manchester United have four key strikers on their summer transfer shortlist, Standard Sport understands.

Welcome to the Evening Standard's live blog covering the latest transfer news and rumours from the Premier League and beyond.

Manchester United fans hailed the fine work of 'agent Marcus Rashford' once more after his FIFA 20 battle with England colleague Jadon Sancho.

Ole Gunnar Solskjaer is hoping to continue his Manchester United rebuild this summer with a number of targets already identified.

Welcome to the Evening Standard's live blog covering the latest transfer news and rumours from the Premier League and beyond.

Pierre-Emerick Aubameyang has been warned by a former Gunner than moving to a club like Manchester United at this stage of his career is a riskier prospect than staying at Arsenal.

Jack Wilshere has admitted his transfer to West Ham "hasn't worked out" as he had hoped amid uncertainty over his future at the club.

Welcome to the Evening Standard's live blog covering the latest transfer news and rumours from the Premier League and beyond.

Tottenham have no interest in selling star striker Harry Kane to Manchester United this summer.

Manchester United fans are growing increasingly excited that Jadon Sancho could be on his way to Old Trafford this summer after the Borussia Dortmund star's latest hint.

Jadon Sancho's future looks set to be a long-running story throughout the summer.

Jadon Sancho's future looks set to be a long-running story throughout the summer.

Ivan Rakitic has warned Barcelona he wants to be "where he is valued" amid growing transfer speculation.

Frank Lampard has revealed Chelsea are ready to execute various different transfer plans depending on the impact of the coronavirus pandemic.

Welcome to the Evening Standard's live blog covering the latest transfer news and rumours from the Premier League and beyond.

The current break due to coronavirus has seen the rumour mill in overdrive. With no football happening on the pitch, transfer talk is dominating the sports pages.

Ole Gunnar Solskjaer is hoping to continue his Manchester United rebuild this summer with a number of targets already identified.

Donny van de Beek's agent believes his client will still be able to secure a move away from Ajax this summer.

Welcome to the Evening Standard's live blog covering the latest transfer news and rumours from the Premier League and beyond.

Harry Kane's departure from Tottenham is "inevitable", according to former West Ham player Tony Cottee.

Victor Osimhen has opened up about why he rejected Arsenal as a teenager... and why he will use the same reasoning when it comes to his next move.

Kai Havertz is open to leaving Germany amid transfer interest from Manchester United, along with links to a host of other top European clubs.

Welcome to the Evening Standard's live blog covering the latest transfer news and rumours from the Premier League and beyond.

Barcelona coach Quique Setien believes Philippe Coutinho is a 'great player' and says he is 'counting on' the 27-year-old for next season.

German legend Lothar Matthaus has advised Dayot Upamecano to remain at RB Leipzig despite significant interest from a plethora of European giants.

Welcome to the Evening Standard's live blog covering the latest transfer news and rumours from the Premier League and beyond.

Former Premier League Golden Boot winner Kevin Phillips believes Harry Kane would be a "wonderful fit" for Manchester United.

Liverpool have been warned Sadio Mane will not stay at the club "forever" by his Senegal team-mate Keita Balde.

Paul Merson has said 'anyone expecting £200m can forget it'