Buchanan C E, Strominger J L
Proc Natl Acad Sci U S A. 1976 Jun;73(6):1816-20. doi: 10.1073/pnas.73.6.1816.
Penicillin- (cloxacillin-) resistant mutants of Bacillus subtilis were isolated in a stepwise fashion and the five penicillin-binding components (PBCs) in each were examined to determine which of the proteins, if any, corresponds to the penicillin killing site. PBCs II and V were previously eliminated as the likely penicillin targett. In the present work, PBC IV showed no change in sensitivity to cloxacillin in any of the resistant mutants isolated. PBC I did not change until the fifth-step mutant, in which it could not be detected by penicillin binding. Since PBC I did not bind penicillins that are lethal for this mutant, it also cannot be the lethal target. PBC II showed increased resistance to cloxacillin in three discrete steps, i.e., in mutants 1, 4, and 5, accompanied by changes in its electrophoretic mobility. However, the sensitivity of PBC II to penicillin G changed very little. Correspondingly, the cloxacillin-resistant mutants were unaltered in their sensitivity to penicillin G in vivo. Thus, of the five PBCs found in B. subtilis, PBC II is the most likely target for killing by penicillins.
枯草芽孢杆菌对青霉素（氯唑西林）耐药的突变体是通过逐步筛选分离得到的，并且对每个突变体中的五种青霉素结合成分（PBCs）进行了检测，以确定这些蛋白质中是否有任何一种与青霉素的致死位点相对应。PBCs II和V之前已被排除作为可能的青霉素靶点。在本研究中，在分离得到的任何耐药突变体中，PBC IV对氯唑西林的敏感性均未发生变化。直到第五步突变体，PBC I才发生变化，在该突变体中通过青霉素结合无法检测到它。由于PBC I不结合对该突变体具有致死性的青霉素，因此它也不可能是致死靶点。PBC II在三个不同步骤中对氯唑西林的耐药性增加，即在突变体1、4和5中，同时其电泳迁移率也发生了变化。然而，PBC II对青霉素G的敏感性变化很小。相应地，对氯唑西林耐药的突变体在体内对青霉素G的敏感性未发生改变。因此，在枯草芽孢杆菌中发现的五种PBCs中，PBC II最有可能是青霉素致死的靶点。
