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 residues of the Escherichia coli penicillin-binding protein 3 were each converted into an alanine residue. As deduced from penicillin-binding and complementation experiments, none of these dicarboxylic acid residues 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.