Dataset Information

Regulation of peptidoglycan synthesis by outer-membrane proteins.

ABSTRACT: Growth of the mesh-like peptidoglycan (PG) sacculus located between the bacterial inner and outer membranes (OM) is tightly regulated to ensure cellular integrity, maintain cell shape, and orchestrate division. Cytoskeletal elements direct placement and activity of PG synthases from inside the cell, but precise spatiotemporal control over this process is poorly understood. We demonstrate that PG synthases are also controlled from outside of the sacculus. Two OM lipoproteins, LpoA and LpoB, are essential for the function, respectively, of PBP1A and PBP1B, the major E. coli bifunctional PG synthases. Each Lpo protein binds specifically to its cognate PBP and stimulates its transpeptidase activity, thereby facilitating attachment of new PG to the sacculus. LpoB shows partial septal localization, and our data suggest that the LpoB-PBP1B complex contributes to OM constriction during cell division. LpoA/LpoB and their PBP-docking regions are restricted to ?-proteobacteria, providing models for niche-specific regulation of sacculus growth.

SUBMITTER: Typas A

PROVIDER: S-EPMC3060616 | biostudies-literature | 2010 Dec

REPOSITORIES: biostudies-literature

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Regulation of peptidoglycan synthesis by outer-membrane proteins.

Typas Athanasios A Banzhaf Manuel M van den Berg van Saparoea Bart B Verheul Jolanda J Biboy Jacob J Nichols Robert J RJ Zietek Matylda M Beilharz Katrin K Kannenberg Kai K von Rechenberg Moritz M Breukink Eefjan E den Blaauwen Tanneke T Gross Carol A CA Vollmer Waldemar W

Cell 20101201 7

Growth of the mesh-like peptidoglycan (PG) sacculus located between the bacterial inner and outer membranes (OM) is tightly regulated to ensure cellular integrity, maintain cell shape, and orchestrate division. Cytoskeletal elements direct placement and activity of PG synthases from inside the cell, but precise spatiotemporal control over this process is poorly understood. We demonstrate that PG synthases are also controlled from outside of the sacculus. Two OM lipoproteins, LpoA and LpoB, are e ...[more]

PMID: 21183073

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Project description:Gram-negative bacteria resist external stresses due to cell envelope rigidity, which is provided by two membranes and a peptidoglycan layer. The outer membrane (OM) surface contains lipopolysaccharide (LPS; contains O-antigen) or lipooligosaccharide (LOS). LPS/LOS are essential in most Gram-negative bacteria and may contribute to cellular rigidity. Acinetobacter baumannii is a useful tool for testing these hypotheses as it can survive without LOS. Previously, our group found that strains with naturally high levels of penicillin binding protein 1A (PBP1A) could not become LOS deficient unless the gene encoding it was deleted, highlighting the relevance of peptidoglycan biosynthesis and suggesting that high PBP1A levels were toxic during LOS deficiency. Transposon sequencing and follow-up analysis found that axial peptidoglycan synthesis by the elongasome and a peptidoglycan recycling enzyme, ElsL, were vital in LOS-deficient cells. The toxicity of high PBP1A levels during LOS deficiency was clarified to be due to a negative impact on elongasome function. Our data suggest that during LOS deficiency, the strength of the peptidoglycan specifically imparted by elongasome synthesis becomes essential, supporting that the OM and peptidoglycan contribute to cell rigidity. IMPORTANCE Gram-negative bacteria have a multilayered cell envelope with a layer of cross-linked polymers (peptidoglycan) sandwiched between two membranes. Peptidoglycan was long thought to exclusively provide rigidity to the cell providing mechanical strength. Recently, the most outer membrane of the cell was also proposed to contribute to rigidity due to properties of a unique molecule called lipopolysaccharide (LPS). LPS is located on the cell surface in the outer membrane and is typically required for growth. By using Acinetobacter baumannii, a Gram-negative bacterium that can grow without LPS, we found that key features of the peptidoglycan structure also become essential. This finding supports that both the outer membrane and peptidoglycan contribute to cell rigidity.

Dataset Information

Regulation of peptidoglycan synthesis by outer-membrane proteins.

Publications

Regulation of peptidoglycan synthesis by outer-membrane proteins.

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