Furazlocillin binds selectively to penicillin-binding protein 3 (PBP-3), prevents septation of Escherichia coli, and allows the cells to form long fiaments without lysis. The effect offurazlocillin on the morphology, autolysis, and murein synthesis of E. coli mutants deficient in either PBP-1A, PBP-lBs, or PBP-2 was studied. The results reveal that PBP-1A and PBP-lBs functions are not equivalent since furazlocillin affects the morphology, autolysis, and murein synthesis of PBP1Amutants quite differently from that of PBP-lBs mutants. Different "PBP-2-" mutants were found to respond to furazlocillin in dramatically different ways: strain LS-1 cells formed elongated rods with a central bulge which eventually lysed, whereas SP6 cells formed stable "barbells" in which the two daughter cells were well separated but remained connnected by a thick central region.At least nine penicillin-binding proteins (PBPs), located in the cytoplasmic membrane of Escherichia coli, can be detected with radiolabeled benzylpenicillin by a sodium. dodecyl sul-
During diaminopimelic acid starvation of Escherichia coli W7, a large fraction of the preexisting murein cross-links are opened by murein endopeptidase and the resulting uncross-linked material is degraded. This is reflected morphologically in a general loss of rigidity of the murein sacculus long before lysis occurs. In growing cells, a dynamic situation is demonstrable. When cells whose murein sacculi are uniformly labeled with [14C]diaminopimelic acid were chased with unlabeled DAP, a significant, rapid shift of [14C]diaminopimelic acid from the donor to the acceptor half of dimers was observed. The shift can be explained by the presence of about 100 separate sites where new murein strands were being inserted between old radioactive strands of murein. Thus, the gradual loss of rigidity of the murein sacculus as endopeptidase continues to function during starvation of E. coli W7 suggests an even distribution of the active endopeptidases. This is consistent with the kinetic data which suggest that endopeptidase, along with murein synthetase and transpeptidase, acts at about 100 distinct sites to elongate the murein sacculus.on July 31, 2020 by guest
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