Structural basis of malodour precursor transport in the human axilla

Abstract

Mammals produce volatile odours that convey different types of societal information. In Homo sapiens, this is now recognised as body odour, a key chemical component of which is the sulphurous thioalcohol, 3-methyl-3-sulfanylhexan-1-ol (3M3SH). Volatile 3M3SH is produced in the underarm as a result of specific microbial activity, which act on the odourless dipeptide-containing malodour precursor molecule, S-Cys-Gly-3M3SH, secreted in the axilla (underarm) during colonisation. The mechanism by which these bacteria recognise S-Cys-Gly-3M3SH and produce body odour is still poorly understood. Here we report the structural and biochemical basis of bacterial transport of S-Cys-Gly-3M3SH by Staphylococcus hominis, which is converted to the sulphurous thioalcohol component 3M3SH in the bacterial cytoplasm, before being released into the environment. Knowledge of the molecular basis of precursor transport, essential for body odour formation, provides a novel opportunity to design specific inhibitors of malodour production in humans.

Structural basis for prodrug recognition by the SLC15 family of proton coupled peptide transporters

“…It is unclear whether this is due to the presence of the ketomethylene group replacing the peptide bond or the absence of side chains that would be accommodated within the specificity pockets found in the binding sites. A similar vertical orientation was observed for a bound thioalcohol peptide, Cys-Gly-3M3SH, in our previous structure of PepT Sh (33) and a common set of interactions between these three ligands can be discerned, being made to Y41 and N167 (SI Figure 11), which are strictly conserved throughput the SLC15 family (SI Figure 2). To a lesser extent we also observe interactions to N347, the backbone carbonyl of Q344 and several ordered water molecules, which also play an important role in proton movement within peptide transporters (50).…”

“…Following extensive screening, a crystal structure of PepT Sh in complex with valacyclovir was subsequently determined using the in meso crystallisation method (36) and refined to a final resolution of 3.1 Å ( SI Table1 ). PepT Sh adopts an almost identical inward open conformation to that obtained in our previous study (33), with a root mean square deviation (r.m.s.d) of 0.499 Å for 480 C β atoms ( Figure 2A ). The valacyclovir drug molecule was clearly observed sitting in the central peptide binding site, coordinating a single water molecule ( Figure 2B ).…”

“…Recently we discovered a prokaryotic homologue of PepT1 from the bacterium Staphylococcus hominis , PepT Sh , which was able to transport a natural thioalcohol conjugated peptide, exhibiting structural characteristics similar to prodrug molecules ( SI Figure 2 ) (33). We therefore reasoned that PepT Sh may also be able to recognise and transport valacyclovir.…”

The conformational distribution of a major facilitator superfamily peptide transporter is modulated by the membrane composition

“…POTs have been extensively studied by x-ray crystallography and biochemical transport assays over the past years 27,36,39,59,70,73,83,84 . Numerous structures of various bacterial homologues in the absence and presence of substrates, drugs, and prodrugs are available, highlighting crucial residues for substrate binding and proton coupling [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58] . Unfortunately, only inward-open and partially inward-open states of POTs have so far been described at atomic resolution and the influence of the membrane environment on structure and transport has been neglected 41,42,47,52,53,55,58 .…”

“…Their remarkable substrate promiscuity 38,39 together with their highly abundant MFS fold 40 makes them ideal models to understand the interplay between conformational changes and transport. Numerous bacterial POT structures have been determined to date [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58] . We focus on the E. coli peptide transporter DtpA 59,60 to explore the effect of different environments such as detergents and Saposin nanoparticles 61,62 (SapNPs) with different lipid compositions on the conformation of the protein using single molecule FRET (smFRET) [63][64][65][66][67][68] .…”