Molecular divergence of a major peptidoglycan synthetase with transglycosylase - transpeptidase activities in Escherichia coli — Penicillin-binding protein 1Bs

Abstract

Penicillin-binding protein 1Bs of Escherichia coli (Mr ca. 9 × 10 4) gave three protein bands with slightly different mobilities on sodium dodecylsulfate — polyacrylamide gel electrophoresis. The enzymatic activities of each of these proteins were identified after renaturation of the proteins separated by electrophoresis. Each of them had two enzymatic activities of the last steps of synthesis of peptidoglycan from lipid-linked precursor, i. e., activity of transglycosylase, which extends the glycan chain, and activity of penicillin-sensitive transpeptidase, which crosslinks glycan chains with peptide cross-bridges. Trypsin treatment of each of the three proteins resulted in formation of a doublet of penicillin-binding proteins (Mr ca. 5 × 10 4). The results strongly indicate that penicillin-binding protein 1Bs are bifunctional peptidoglycan synthetase proteins differing slightly in molecular structure.