Fig 1. WTA biosynthesis pathway.

WTA is sequentially synthesized by a series of Tar enzymes on a bactoprenyl phosphate carrier on the inner leaflet of the cell membrane and eventually transported to the outer leaflet where it is cross-linked to peptidoglycan. See inset for details. Non-essential early steps in WTA biosynthesis are shown as green arrows, late stage conditionally essential steps are shown as purple arrows. Note, MnaA is highlighted by a dashed bidirectional green arrow, highlighting its novel functional role as an epimerase that interconverts UDP-GlcNAc and UDP-ManNAc, thus providing substrates for TarO and TarA, respectively. L638 is a Staphylococcal-specific TarG inhibitor [33]. Schematic has been adapted from [34].