Summary
A bioRxiv preprint reports that three enzymes in Escherichia coli release polysaccharide cargo from the lipid carrier undecaprenyl. The findings connect carrier recycling to several bacterial cell-envelope pathways.
A bioRxiv preprint reports that three enzymes in Escherichia coli release sugar-based building blocks from undecaprenyl, a lipid carrier used to move precursors for bacterial cell-envelope construction. The researchers name the enzymes UprA, UprB and UprC, and propose that they help return the carrier to circulation after its cargo has been delivered.
The carrier, also called C55, is shared by multiple envelope-building pathways. Because the available pool is finite, releasing completed or growing polysaccharide cargo allows undecaprenyl to be reused. The authors describe the newly identified enzymes as periplasmic proteins that break the bond between the carrier and its attached polysaccharide precursor.
Three enzymes, different pathways
The preprint assigns each enzyme a distinct role. UprA releases elongating peptidoglycan glycan strands from the inner membrane. Peptidoglycan is the mesh-like material that gives bacterial cells structural support; the authors describe this release as the long-sought terminal step in its synthesis.
UprB cleaves the carrier-linked initiating unit shared by the enterobacterial common antigen and O-antigen pathways. UprC is described as the likely release factor for the colanic acid pathway. These assignments connect carrier recycling to several different parts of envelope assembly rather than to a single polysaccharide route.
A shared mechanism and a possible drug target
The researchers place UprA, UprB and UprC in a widespread family of related proteins previously known as DUF218. They report that the proteins share a conserved catalytic core, suggesting a common chemical mechanism for releasing different polysaccharide cargoes.
That shared feature could be relevant to antibiotic research: the authors identify the family as a potential target for drugs that disrupt multiple envelope pathways at once. This is a proposed direction, rather than a reported antibiotic treatment. The work is presented as a preprint, and UprC’s role is specifically described as likely.