PgpB

PgpB, short for phosphatidylglycerophosphatase B, is an integral membrane enzyme found in many bacteria. It belongs to the PAP2 lipid phosphate phosphatase family and functions to dephosphorylate phosphatidylglycerophosphate (PGP) to produce phosphatidylglycerol (PG), a key step in the biosynthesis and remodeling of phospholipids in the inner membrane.

In Escherichia coli and many other bacteria, PgpB is predicted to be a multi-pass inner membrane protein, commonly with six transmembrane helices. The catalytic site resides in periplasmic loops and depends on divalent metal ions, typically Mg2+ or Mn2+, for activity. The enzyme shows specificity for PGP but is broadly related to other lipid phosphatases in the PAP2 family.

PgpB acts in concert with other PGP phosphatases, such as PgpA and PgpC, to dephosphorylate PGP. In organisms that encode multiple enzymes, single-gene deletions often produce modest phenotypes due to redundancy; double or triple mutants can exhibit growth or envelope defects, particularly under stress or altered membrane conditions.

The gene encoding PgpB is widely conserved among Gram-negative bacteria and is present in some Gram-positive species as well. Structural studies, including X-ray crystallography of bacterial PgpB homologs, have illuminated the arrangement of transmembrane segments and the location of the catalytic machinery, advancing understanding of the dephosphorylation mechanism.

PgpB is of interest not only for basic cell biology and lipid metabolism but also as a potential target in antimicrobial strategies aimed at perturbing membrane biogenesis.