title: On the process of cellular division in Escherichia coli: isolation and characterization of penicillin-binding proteins 1a, 1b, and 3.
abstract: Multiple mutants of Escherichia coli defective in penicillin-binding proteins (PBPs) were constructed, and into these strains Co1E1 plasmids carrying the genes for PBP-1a, -1b, or -3 were introduced. From these plasmid-carrying strains, PBP-1a and -1b were purified by ampicillin-Sepharose affinity chromatography and PBP-3 by cephalexin-Sepharose affinity chromatography. Improved purification was achieved by differential elution with NH2OH. Purified PBP-1b synthesized murein when added to the membrane fraction of a PBP-1b-defective mutant, which by itself failed to support murein synthesis in vitro. The PBP-1b preparation was able to synthesize murein from the lipid intermediate extracted with chloroform/methanol but was unable to utilize UDP-linked precursors for murein synthesis. Murein synthesis was inhibited by vancomysin, ristocetin, moenomycin, and enduracidin, but not by beta-lactam antibiotics. The synthesized murein was shown to contain crosslinked muropeptides. Their crosslinking was abolished by action of beta-lactam antibiotics. The PBP-1a and -3 preparations showed substantially no activity for murein synthesis in the same reaction system. None of the three PBPs showed D-alanine carboxypeptidase activity with UDP-N-acetylmuramoyl-pentapeptide as substrate or endopeptidase activity with bis(disaccharide-peptide) as substrate.
mesh_terms: D001426:Bacterial Proteins / Q000302:isolation & purification*; D002352:Carrier Proteins / Q000378:metabolism; D002455:Cell Division; D002846:Chromatography, Affinity; D004926:Escherichia coli / Q000166:cytology* / Q000378:metabolism; D009154:Mutation; D010406:Penicillins / Q000378:metabolism*; D010457:Peptidoglycan / Q000096:biosynthesis*; D010957:Plasmids
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D010406:Penicillins; D010457:Peptidoglycan