Abstract
SummaryPeptidoglycan (PG) is an essential component of the bacterial cell wall and is assembled from a lipid II precursor by glycosyltransferase and transpeptidase reactions catalyzed in particular by bifunctional class A penicillin-binding proteins (aPBPs). In the major clinical pathogen Pseudomonas aeruginosa, PBP1B is anchored within the cytoplasmic membrane but regulated by a bespoke outer membrane-localized lipoprotein known as LpoP. Here, we report the structure of LpoP, showing an extended N-terminal, flexible tether followed by a well-ordered C-terminal tandem-tetratricopeptide repeat domain. We show that LpoP stimulates both PBP1B transpeptidase and glycosyltransferase activities in vitro and interacts directly via its C terminus globular domain with the central UB2H domain of PBP1B. Contrary to the situation in E. coli, P. aeruginosa CpoB does not regulate PBP1B/LpoP in vitro. We propose a mechanism that helps to underscore similarities and differences in class A PBP activation across Gram-negative bacteria.
Highlights
The biosynthesis of the bacterial cell wall is an excellent target for antibacterial therapy, as exemplified by the clinical action of b-lactam antibiotics, which inhibit one of the final steps in the pathway of peptidoglycan (PG) biosynthesis
To further dissect the P. aeruginosa PBP1B (PaPBP1B)-LpoP interaction, we show that the UB2H domain of PaPBP1B interacts with the C terminus of LpoP and use NMR
Commonalities between LpoB- and LpoP-Based Systems We show that the domain organization of LpoP is consistent with the model that it serves to activate PaPBP1B in an analogous manner to that by which LpoB activates EcPBP1B
Summary
The biosynthesis of the bacterial cell wall is an excellent target for antibacterial therapy, as exemplified by the clinical action of b-lactam antibiotics, which inhibit one of the final steps in the pathway of peptidoglycan (PG) biosynthesis. PG is comprised of polymerized glycan strands of alternating, b-1,4-linked N-acetylglucosamine and N-acetylmuramic acid. Class A penicillin-binding proteins (aPBPs) are the critical and principal PG synthase for proper cell wall assembly and cell integrity in most bacteria where they have been investigated (Cho et al, 2016). These bifunctional enzymes perform, in distinct active sites, both the glycosyltransferase (GTase) activity, which polymerizes glycan strands from lipid II, and a DD-transpeptidase (TPase) activity, which cleaves a DAla4-D-Ala peptide bond of the acyl donor and transfers the
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