Two distinct transpeptidation reactions during murein synthesis in Escherichia coli.
Murein synthesized in ether-permeabilized cells of Escherichia coli deficient in individual penicillin-binding proteins (PBPs) and in the presence of certain beta-lactam antibiotics was analyzed by high-pressure liquid chromatography separation of the muramidase split products. PBP 1b was found to to be the major murein synthesizing activity that was poorly compensated for by PBP 1a. A PBP 2 mutant as well as mecillinam-inhibited cells showed increased activity in the formation of oligomeric muropeptides as well as UDP-muramylpeptidyl-linked muropeptides, the reaction products of transpeptidation, bypassing the lipid intermediate. In contrast, penicillin G and furazlocillin severely inhibited these reactions but stimulated normal dimer production. It is concluded that two distinct transpeptidases exist in E. coli: one, highly sensitive to penicillin G and furazlocillin, catalyzes the formation of hyper-cross-linked muropeptides, and a second one, quite resistant to these antibiotics, synthesizes muropeptide dimers.
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D000560:Amdinocillin / Q000494:pharmacology; D001390:Azlocillin / Q000031:analogs & derivatives / Q000494:pharmacology; D001426:Bacterial Proteins; D002352:Carrier Proteins / Q000502:physiology; D002455:Cell Division; D004926:Escherichia coli / Q000254:growth & development / Q000378:metabolism*; D006602:Hexosyltransferases; D048289:Imidazolidines; D002267:Muramoylpentapeptide Carboxypeptidase / Q000502:physiology; D046915:Penicillin-Binding Proteins; D010406:Penicillins / Q000494:pharmacology; D010457:Peptidoglycan / Q000096:biosynthesis*; D010458:Peptidyl Transferases / Q000378:metabolism
D001426:Bacterial Proteins; D002352:Carrier Proteins; D048289:Imidazolidines; D046915:Penicillin-Binding Proteins; D010406:Penicillins; D010457:Peptidoglycan; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase; D001390:Azlocillin; C017976:furazlocillin; D000560:Amdinocillin