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Differential Responses of Escherichia coli Cells Expressing Cytoplasmic Domain Mutants of Penicillin-Binding Protein 1b after Impairment of Penicillin-Binding Proteins 1a and 3

By Christian Chalut, Xavier Charpentier, Marie-Hélène Remy and Jean-Michel Masson


Penicillin-binding protein 1b (PBP1b) is the major high-molecular-weight PBP in Escherichia coli. Although it is coded by a single gene, it is usually found as a mixture of three isoforms which vary with regard to the length of their N-terminal cytoplasmic tail. We show here that although the cytoplasmic tail seems to play no role in the dimerization of PBP1b, as was originally suspected, only the full-length protein is able to protect the cells against lysis when both PBP1a and PBP3 are inhibited by antibiotics. This suggests a specific role for the full-length PBP1b in the multienzyme peptidoglycan-synthesizing complex that cannot be fulfilled by either PBP1a or the shorter PBP1b proteins. Moreover, we have shown by alanine-stretch-scanning mutagenesis that (i) residues R11 to G13 are major determinants for correct translocation and folding of PBP1b and that (ii) the specific interactions involving the full-length PBP1b can be ascribed to the first six residues at the N-terminal end of the cytoplasmic domain. These results are discussed in terms of the interactions with other components of the murein-synthesizing complex

Topics: Enzymes and Proteins
Publisher: American Society for Microbiology
Year: 2001
DOI identifier: 10.1128/JB.183.1.200-206.2001
OAI identifier:
Provided by: PubMed Central
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