Several distinct localization patterns for penicillin‐binding proteins in Bacillus subtilis

Abstract

SummaryBacterial cell shape is determined by a rigid external cell wall. In most non-coccoid bacteria, this shape is also determined by an internal cytoskeleton formed by the actin homologues MreB and/or Mbl. To gain further insights into the topological control of cell wall synthesis in bacteria, we have constructed green fluorescent protein (GFP) fusions to all 11 penicillinbinding proteins (PBPs) expressed during vegetative growth of Bacillus subtilis . The localization of these fusions was studied in a wild-type background as well as in strains deficient in FtsZ, MreB or Mbl. PBP3 and PBP4a localized specifically to the lateral wall, in distinct foci, whereas PBP1 and PBP2b localized specifically to the septum. All other PBPs localized to both the septum and the lateral cell wall, sometimes with irregular distribution along the lateral wall or a preference for the septum. This suggests that cell wall synthesis is not dispersed but occurs at specific places along the lateral cell wall. The results implicate PBP3, PBP5 and PBP4a, and possibly PBP4, in lateral wall growth. Localization of PBPs to the septum was found to be dependent on FtsZ, but the GFP-PBP fluorescence patterns were not detectably altered in the absence of MreB or Mbl.

Crystal Structure of the Actinomadura R39 DD-peptidase Reveals New Domains in Penicillin-binding Proteins

“…The resemblance of the R39 domain II topology with E. coli d-Tyr-tRNA Tyr deacylase and barley 1,3-1,4-␤-glucanase is astonishing but seems unlikely to be associated with the functional properties of these enzymes. Although B. subtilis PBP4a was shown to be absent from the septum site (49), it is interesting that interactions between proteins of the septation machinery and minor peptidoglycan-modifying enzymes have been shown to be responsible for significant aspects of bacterial shape determinations (50). Although very limited, the resemblance of R39 domain II to the N-terminal domain of MinC and the 1A region of FtsA, two proteins involved in the regulation of septum formation, suggests that class C low molecular mass PBPs could interact with a protein of the septation machinery.…”

Crystal Structures of Complexes of Bacterial dd-Peptidases with Peptidoglycan-Mimetic Ligands: The Substrate Specificity Puzzle

“…34,35 The latter of these enzymes has also been shown to have high hydrolytic activity against the peptide 7. 18 There is no doubt that E. coli PBP5 does participate in bacterial cell wall construction and/or maintenance.…”

Dynamic localization of membrane proteins in Bacillus subtilis

“…The presence of chemoreceptors at cell poles is well established (Maddock & Shapiro, 1993) and this may reflect a preference of these proteins for acidic lipids such as cardiolipin. Penicillinbinding proteins involved in cell wall synthesis have also been shown to localize in several patterns, including to division septa and discrete foci along the long axis of the cell, reflecting the role of these proteins in specific stages of cell wall synthesis (Scheffers et al, 2004). However, analysis of the localization of the E. coli Sec protein secretion machinery, BglF sugar sensor and B. subtilis phage w29 DNA replication protein p16.7 indicates that these proteins are homogeneously distributed around the cytoplasmic membrane, with no reported preference for cell poles or other observable domains (Brandon et al, 2003;Lopian et al, 2003;Meijer et al, 2001).…”