Impact of participation as a peer change agent on peer change agents themselves: a quantitative study of a peer-led, social media-based PrEP promotion intervention.

Despite the adoption of pre-exposure prophylaxis (PrEP) as a crucial HIV intervention, uptake remains suboptimal among men who have sex with men, a sexual minority group, due to barriers like cost and stigma. Peer change agents (PCAs) disseminate PrEP information within their social networks. This study explores the reciprocal effects of an online community-based participatory intervention on PCAs, focusing on their transformed PrEP uptake perceptions-leadership efficacy, social network dynamics, attitudes, perceived benefits and barriers and self-efficacy.

Diverse HIV viruses are targeted by a conformationally dynamic antiviral.

Rhesus macaque TRIMCyp (RhTC) is a potent primate antiviral host protein that inhibits the replication of diverse HIV viruses. Here we show that it has acquired the ability to target multiple viruses by evolving an active site that interconverts between multiple conformations. Mutations that have relieved active site constraints allow RhTC to dynamically sample conformational space, including radically different conformers that target both HIV-1 and HIV-2 viruses.

Crystal structures of an oligopeptide-binding protein from the biosynthetic pathway of the beta-lactamase inhibitor clavulanic acid.

Clavulanic acid (CA) is a clinically important beta-lactamase inhibitor that is produced by fermentation of Streptomyces clavuligerus. The CA biosynthesis pathway starts from arginine and glyceraldehyde-3-phosphate and proceeds via (3S,5S)-clavaminic acid, which is converted to (3R,5R)-clavaldehyde, the immediate precursor of (3R,5R)-CA. Open reading frames 7 (orf7) and 15 (orf15) of the CA biosynthesis cluster encode oligopeptide-binding proteins (OppA1 and OppA2), which are essential for CA biosynthesis.

Designer enzymes for glycosphingolipid synthesis by directed evolution.

Though glycosphingolipids have great potential as therapeutics for cancer, HIV, neurodegenerative diseases and auto-immune diseases, both extensive study of their biological roles and development as pharmaceuticals are limited by difficulties in their synthesis, especially on large scales. Here we addressed this restriction by expanding the synthetic scope of a glycosphingolipid-synthesizing enzyme through a combination of rational mutagenesis and directed evolution with an ELISA-based screening strategy. We targeted both a low-level promiscuous substrate activity and the overall catalytic efficiency of the catalyst, and we identified several mutants with enhanced activities.

Structural and mechanistic studies on N(2)-(2-carboxyethyl)arginine synthase.

N(2)-(2-Carboxyethyl)arginine synthase (CEAS), an unusual thiamin diphosphate (ThDP)-dependent enzyme, catalyses the committed step in the biosynthesis of the b-lactamase inhibitor clavulanic acid in Streptomyces clavuligerus. Crystal structures of tetrameric CEAS-ThDP in complex with the substrate analogues 5-guanidinovaleric acid (GVA) and tartrate, and a structure reflecting a possible enol(ate)-ThDP reaction intermediate are described. The structures suggest overlapping binding sites for the substrates D-glyceraldehyde-3-phosphate (D-G3P) and L-arginine, and are consistent with the proposed CEAS mechanism in which D-G3P binds at the active site and reacts to form an alpha,beta-unsaturated intermediate,which subsequently undergoes (1,4)-Michael addition with the alpha-amino group of L-arginine.

The structural basis for T-antigen hydrolysis by Streptococcus pneumoniae: a target for structure-based vaccine design.

Streptococcus pneumoniae endo-alpha-N-acetylgalactosaminidase is a cell surface-anchored glycoside hydrolase from family GH101 involved in the breakdown of mucin type O-linked glycans. The 189-kDa mature enzyme specifically hydrolyzes the T-antigen disaccharide from extracellular host glycoproteins and is representative of a broadly important class of virulence factors that have remained structurally uncharacterized due to their large size and highly modular nature. Here we report a 2.

Structural and mechanistic analyses of endo-glycoceramidase II, a membrane-associated family 5 glycosidase in the Apo and GM3 ganglioside-bound forms.

endo-Glycoceramidase, a membrane-associated family 5 glycosidase, deviates from the typical polysaccharide substrate specificity of other soluble members of the family, preferentially hydrolyzing glycosidic linkages between the oligosaccharide and ceramide moieties of gangliosides. Here we report the first x-ray crystal structures of an endo-glycoceramidase from Rhodococcus sp., in the apo form, in complex with the ganglioside G(M3) (Svennerholm ganglioside nomenclature (Svennerholm, L.

The enzymology of clavam and carbapenem biosynthesis.

The enzyme-catalysed reactions involved in formation of the bicyclic clavam and carbapenem nuclei, including beta-amino acid and beta-lactam formation, are discussed and compared with those involved in penicillin and cephalosporin biosynthesis. The common role of unusual oxidation reactions in the biosynthetic pathways and the lack of synthetic reagents available to effect them are highlighted.

Crystal structure and mechanistic implications of N2-(2-carboxyethyl)arginine synthase, the first enzyme in the clavulanic acid biosynthesis pathway.

The initial step in the biosynthesis of the clinically important beta-lactamase inhibitor clavulanic acid involves condensation of two primary metabolites, D-glyceraldehyde 3-phosphate and L-arginine, to give N2-(2-carboxyethyl)arginine, a beta-amino acid. This unusual N-C bond forming reaction is catalyzed by the thiamin diphosphate (ThP2)-dependent enzyme N2-(2-carboxyethyl)arginine synthase. Here we report the crystal structure of N2-(2-carboxyethyl)arginine synthase, complexed with ThP2 and Mg2+, to 2.