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Publication Abstract from PubMed

Actinomadura sp. R39 produces an exocellular DD-peptidase/penicillin-binding protein (PBP) whose primary structure is similar to that of Escherichia coli PBP4. It is characterized by a high beta-lactam-binding activity (second order rate constant for the acylation of the active site serine by benzylpenicillin: k2/K = 300 mm(-1) s(-1)). The crystal structure of the DD-peptidase from Actinomadura R39 was solved at a resolution of 1.8 angstroms by single anomalous dispersion at the cobalt resonance wavelength. The structure is composed of three domains: a penicillin-binding domain similar to the penicillin-binding domain of E. coli PBP5 and two domains of unknown function. In most multimodular PBPs, additional domains are generally located at the C or N termini of the penicillin-binding domain. In R39, the other two domains are inserted in the penicillin-binding domain, between the SXXK and SXN motifs, in a manner similar to "Matryoshka dolls." One of these domains is composed of a five-stranded beta-sheet with two helices on one side, and the other domain is a double three-stranded beta-sheet inserted in the previous domain. Additionally, the 2.4-angstroms structure of the acyl-enzyme complex of R39 with nitrocefin reveals the absence of active site conformational change upon binding the beta-lactams.

Crystal structure of the Actinomadura R39 DD-peptidase reveals new domains in penicillin-binding proteins.,Sauvage E, Herman R, Petrella S, Duez C, Bouillenne F, Frere JM, Charlier P J Biol Chem. 2005 Sep 2;280(35):31249-56. Epub 2005 Jun 29. PMID:15987687^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.