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Updated: Aug 8, 2026

Biochemical and Structural Characterization of the Carbohydrate Transport Substrate-binding-protein SP0092
Published on: October 2, 2017
Structural analysis of an "open" form of PBP1B from Streptococcus pneumoniae
Andrew L Lovering1, Liza De Castro, Daniel Lim
1Department of Biochemistry and Molecular Biology, Center for Blood Research, University of British Columbia, Vancouver, Canada.
Abstract:
The class A PBP1b from Streptococcus pneumoniae is responsible for glycosyltransferase and transpeptidase (TP) reactions, forming the peptidoglycan of the bacterial cell wall. The enzyme has been produced in a stable, soluble form and undergoes time-dependent proteolysis to leave an intact TP domain. Crystals of this TP domain were obtained, diffracting to 2.2 A resolution, and the structure was solved by using molecular replacement. Analysis of the structure revealed an "open" active site, with important conformational differences to the previously determined "closed" apoenzyme. The active-site nucleophile, Ser460, is in an orientation that allows for acylation by beta-lactams. Consistent with the productive conformation of the conserved active-site catalytic residues, adjacent loops show only minor deviation from those of known acyl-enzyme structures. These findings are discussed in the context of enzyme functionality and the possible conformational sampling of PBP1b between active and inactive states.
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