Penicillin-binding protein 1B of Escherichia coli exists in dimeric forms.

A high-molecular-weight band has been detected in Western immunoblots of nonboiled Escherichia coli samples incubated with polyclonal antiserum against penicillin-binding protein 1B (PBP 1B). This band was shown to be a dimer of PBP 1B. The dimer was more strongly associated with the envelope than the monomer, and it was still able to bind penicillin G. Analysis of the binding of fusion proteins of PBP 1B and beta-lactamase showed that the part of PBP 1B necessary for complex formation lies in the amino-terminal half of the protein.