Two broadly conserved families of polyprenyl phosphate transporters

Peptidoglycan and virtually all surface glycopolymers in bacteria are built in the cytoplasm on the lipid carrier undecaprenyl-phosphate (UndP). These UndP-linked precursors are transported across the membrane and polymerized or directly transferred to surface polymers, lipids, or proteins. UndP is then flipped to regenerate the pool of cytoplasmic-facing UndP. The identity of the flippase that catalyzes transport has eluded identification for decades. Here, using the antibiotic amphomycin that targets UndP, we discovered two broadly conserved families that catalyze UndP recycling. One (UptA) is a member of the DedA superfamily; the other (PopT) contains the domain DUF368. We show that family members from gram-positive and gram-negative bacteria catalyze UndP transport in Bacillus subtilis. Inhibitors of these flippases could potentiate the current arsenal of cell envelope-targeting antibiotics.