Moxalactam (6059-S), a new 1-oxa-beta-lactam: binding affinity for penicillin-binding proteins of Escherichia coli K-12.

Moxalactam (6059-S) is a new beta-lactam derivative with a structure markedly different from those of penicillins or cephalosporins. The binding activity of 6059-S to penicillin-binding proteins (PBPs) in Escherichia coli K-12 was tested. [14C]benzylpenicillin- or [14C]6059-S-bound inner membrane proteins of E. coli K-12 were rapidly detected without using fluorography. 6059-S had the highest affinity for PBP-3 and -7/8, had a higher affinity than benzylpenicillin for PBP-1A, -1Bs, -4, and -5/6 and a lower affinity for PBP-2, 609134, the 1-thiacephem analog of 6059-S, showed as high an affinity for PBP-1A, -1Bs, -3, and -4 as 6059-S but a lower affinity for PBP-5/6.