PgpB

=PgpB=

PgpB is an integral membrane protein which catalyses the dephosphorylation of undecaprenyl-pyrophosphate (C55-PP), to form the active undecaprenyl-phosphate (C55-P) lipid carrier (Touze et al, 2008). It belongs to the type 2 phosphatidic acid phosphatase family, identifiable by their characteristic phosphatase signature and distinct, conserved motifs.

__**Structure:**__ It is still unclear as to which side of the cytoplasmic membrane C55-PP dephosphorylation occurs. However, computational models predict that the PgpB protein should contain six transmembrane segments and that the active site faces the periplasm. Further topology analysis, via fusion experiments between truncated forms of PgpB and a beta-lactamase agreed with this (see Vollmer et al, 2008 for full details).



E. coli pgpB mutants were originally isolated during screens to isolate cells defective in phosphotidaglycerol phosphate phosphatase activity. The simultaneous inactivation of the pgpB gene, along with those of the other C55-PP phosphatases ybjG and bacA has been shown to be lethal, via temperature sensitive triple-mutant strains (Touze et al, 2008). However, presence of only one of these three genes is required to sustain normal cell growth
 * __Deletion Mutants:__**

__**Activation:**__ The phosphatase activity of PgpB is activated, indirectly, by phospholipid. It is thought that phospholipids may regulate PgpB phosphatase activity via the rearrangement of long-chain isoprenoids within the membrane, rendering C55-PP a better substrate for PgpB (Vollmer et al, 2008).