SITE-DIRECTED MUTAGENESIS OF DICARBOXYLIC-ACID RESIDUES OF THE PENICILLIN-BINDING MODULE OF THE ESCHERICHIA-COLI PENICILLIN-BINDING PROTEIN-3

The glutamic acid E396, aspartic acid D409 and glutamic acid E411 resi dues of the Escherichia coli penicillin-binding protein 3 were each co nverted into an alanine residue. As deduced from penicillin-binding an d complementation experiments, none of these dicarboxylic acid residue s is involved in the mechanism of acylation by penicillin and none of them is essential for the in vivo functioning of the PBP. The mutation E396, however, causes an increased thermolability of the protein.