Function and Localization Dynamics of Bifunctional Penicillin-Binding Proteins in Caulobacter crescentus

The peptidoglycan cell wall of bacteria is a complex macromolecule composed of glycan strands that are cross-linked by short peptide bridges. Its biosynthesis involves a conserved group of enzymes, the bifunctional penicillin-binding proteins (bPBPs), which contain both a transglycosylase and a tran...

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Published in:	Journal of bacteriology Vol. 196; no. 8; pp. 1627 - 1639
Main Authors:	Strobel, Wolfgang, Möll, Andrea, Kiekebusch, Daniela, Klein, Kathrin E, Thanbichler, Martin
Format:	Journal Article
Language:	English
Published:	United States American Society for Microbiology 01-04-2014
Subjects:	Amino Acid Sequence amino acids bacteria Bacterial proteins Bacteriology Biochemistry Biosynthesis Caulobacter crescentus Caulobacter crescentus - cytology Caulobacter crescentus - enzymology Caulobacter crescentus - growth & development Caulobacter crescentus - physiology cell growth Cell Wall - metabolism cell walls crosslinking cytokinesis Gene Knockout Techniques Microbial Viability Microscopy Molecular Sequence Data morphogenesis N-acetylmuramoyl-L-alanine amidase Penicillin Penicillin-Binding Proteins - genetics Penicillin-Binding Proteins - metabolism Peptidoglycan - biosynthesis peptidoglycans Protein Binding Protein Interaction Mapping proteins
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Summary:	The peptidoglycan cell wall of bacteria is a complex macromolecule composed of glycan strands that are cross-linked by short peptide bridges. Its biosynthesis involves a conserved group of enzymes, the bifunctional penicillin-binding proteins (bPBPs), which contain both a transglycosylase and a transpeptidase domain, thus being able to elongate the glycan strands and, at the same time, generate the peptide cross-links. The stalked model bacterium Caulobacter crescentus possesses five bPBP paralogs, named Pbp1A, PbpC, PbpX, PbpY, and PbpZ, whose function is still incompletely understood. In this study, we show that any of these proteins except for PbpZ is sufficient for growth and normal morphogenesis when expressed at native or elevated levels, whereas inactivation of all five paralogs is lethal. Growth analyses indicate a central role of PbpX in the resistance of C. crescentus against the noncanonical amino acid d-alanine. Moreover, we show that PbpX and PbpY localize to the cell division site. Their recruitment to the divisome is dependent on the essential cell division protein FtsN and likely involves interactions with FtsL and the putative peptidoglycan hydrolase DipM. The same interaction pattern is observed for Pbp1A and PbpC, although these proteins do not accumulate at midcell. Our findings demonstrate that the bPBPs of C. crescentus are, to a large extent, redundant and have retained the ability to interact with the peptidoglycan biosynthetic machineries responsible for cell elongation, cytokinesis, and stalk growth. Nevertheless, they may preferentially act in specific peptidoglycan biosynthetic complexes, thereby facilitating the independent regulation of distinct growth processes.
Bibliography:	http://dx.doi.org/10.1128/JB.01194-13 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Present address: Andrea Möll, Division of Infectious Diseases, Brigham and Women's Hospital and Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts, USA. W.S. and A.M. contributed equally to this paper.
ISSN:	0021-9193 1098-5530
DOI:	10.1128/JB.01194-13