Host-specific enzyme-substrate interactions in SPM-1 metallo-?-lactamase are modulated by second sphere residues.

ABSTRACT: Pseudomonas aeruginosa is one of the most virulent and resistant non-fermenting Gram-negative pathogens in the clinic. Unfortunately, P. aeruginosa has acquired genes encoding metallo-?-lactamases (M?Ls), enzymes able to hydrolyze most ?-lactam antibiotics. SPM-1 is an M?L produced only by P. aeruginosa, while other M?Ls are found in different bacteria. Despite similar active sites, the resistance profile of M?Ls towards ?-lactams changes from one enzyme to the other. SPM-1 is unique among pathogen-associated M?Ls in that it contains "atypical" second sphere residues (S84, G121). Codon randomization on these positions and further selection of resistance-conferring mutants was performed. MICs, periplasmic enzymatic activity, Zn(II) requirements, and protein stability was assessed. Our results indicated that identity of second sphere residues modulates the substrate preferences and the resistance profile of SPM-1 expressed in P. aeruginosa. The second sphere residues found in wild type SPM-1 give rise to a substrate selectivity that is observed only in the periplasmic environment. These residues also allow SPM-1 to confer resistance in P. aeruginosa under Zn(II)-limiting conditions, such as those expected under infection. By optimizing the catalytic efficiency towards ?-lactam antibiotics, the enzyme stability and the Zn(II) binding features, molecular evolution meets the specific needs of a pathogenic bacterial host by means of substitutions outside the active site.

SUBMITTER: Gonzalez LJ 

PROVIDER: S-EPMC3879351 | biostudies-literature | 2014 Jan

REPOSITORIES: biostudies-literature