Penicillin binding protein 2x as a major contributor to intrinsic beta-lactam resistance of Streptococcus pneumoniae.

The production and purification to protein homogeneity of a soluble form of PBP2x from a cefotaxime-resistant Streptococcus pneumoniae strain is reported. It was obtained by a site-directed deletion of the membrane anchor in the corresponding gene, a method similar to that successfully utilized for the production of PBP2x from a cefotaxime-sensitive wild type strain. The kinetic parameters characterizing the interactions of both cefotaxime-resistant and -sensitive proteins have been determined and compared. The results are in agreement with the identification of PBP2x as the primary target for cefotaxime in the sensitive strain and as probably one of several targets in the resistant strain.