title: Mutations affecting penicillin-binding proteins 2a, 2b and 3 in Bacillus subtilis alter cell shape and peptidoglycan metabolism.
abstract: Bacillus subtilis mutants with altered penicillin-binding proteins (PBPs), or altered expression of PBPs, were isolated by screening for changes in susceptibility to beta-lactam antibiotics. Mutations affecting only PBPs 2a, 2b and 3 were isolated. Cell shape and peptidoglycan metabolism were examined in representative mutants. Cells of a PBP 2a mutant (UB8521) were usually twisted whereas PBP 2b (UB8524) and 3 (UB8525) mutants produced helices, particularly after growth at 41 degrees C. The PBP 2a mutant (UB8521) had a higher peptidoglycan synthetic activity than its parent strain whereas the opposite applied to the PBP 2b mutant UB8524. The PBP 3 mutant (UB8525) had a similar peptidoglycan synthetic activity to that of the parent strain when grown at 37 degrees C, but 40% higher activity after growth at 41 degrees C. The PBP 2a mutant (UB8521) exhibited the same wall thickening activity as the parent, but the PBP 2b and 3 mutants (UB8524 and UB8525) were partially defective in this respect. The changes in the susceptibility of PBP 2a, 2b and 3 mutants to beta-lactam antibiotics imply that these PBPs are killing targets, consistent with the fact that these PBPs are also important for shape determination and peptidoglycan synthesis.
mesh_terms: D000217:Acyltransferases / Q000378:metabolism*; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001412:Bacillus subtilis / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D001426:Bacterial Proteins; D002352:Carrier Proteins; D006602:Hexosyltransferases / Q000378:metabolism*; D007769:Lactams; D008826:Microbial Sensitivity Tests; D008855:Microscopy, Electron, Scanning; D009097:Multienzyme Complexes / Q000378:metabolism*; D002267:Muramoylpentapeptide Carboxypeptidase; D009154:Mutation; D046915:Penicillin-Binding Proteins; D010457:Peptidoglycan / Q000096:biosynthesis; D010458:Peptidyl Transferases / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002352:Carrier Proteins; D007769:Lactams; D009097:Multienzyme Complexes; D046915:Penicillin-Binding Proteins; D010457:Peptidoglycan; D000217:Acyltransferases; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase