This model describes a 25-residue domain that includes a near-invariant Pro-Glu-Pro (PEP) motif, a thirteen residue strongly hydrophobic sequence likely to span the membrane, and a five-residue strongly basic motif that often contains multiple Arg residues. In nearly every case, this motif is found within nine residues, and usually within five residues, of the extreme C-terminus of the protein. Proteins with this motif typically have Sec translocation signal sequences at the N-terminus. The PEP-CTERM region typically appears many times per genome (sometimes on over 100 proteins), or not at all, and co-occurs always with an exosortase, analogous (but unrelated) to sortase, the transpeptidase that processes LPXTG sorting signals in Gram-positive bacteria. PEP-CTERM proteins frequently are poorly conserved, low complexity, Ser/Thr-rich proteins that show little resemblance to typical enzymes. Those PEP-CTERM proteins likely undergo extensive glycosylation and then constitute much of the proteinaceous matter that is often found in the extracellular polymeric substance (EPS) of environmental bacterial biofilms.
GO Terms:- Cellular Component:
- external side of cell outer membrane (GO:0031240)
- Date:
- 2023-07-12