Send to

Choose Destination
See comment in PubMed Commons below
Protein Sci. 2001 Dec;10(12):2556-65.

Identification of residues critical for metallo-beta-lactamase function by codon randomization and selection.

Author information

Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas 77030, USA.


IMP-1 beta-lactamase is a zinc metallo-enzyme encoded by the transferable bla(IMP-1) gene, which confers resistance to virtually all beta-lactam antibiotics including carbapenems. To understand how IMP-1 recognizes and hydrolyzes beta-lactam antibiotics it is important to determine which amino acid residues are critical for catalysis and which residues control substrate specificity. We randomized 27 individual codons in the bla(IMP-1) gene to create libraries that contain all possible amino acid substitutions at residue positions in and near the active site of IMP-1. Mutants from the random libraries were selected for the ability to confer ampicillin resistance to Escherichia coli. Of the positions randomized, >50% do not tolerate amino acid substitutions, suggesting they are essential for IMP-1 function. The remaining positions tolerate amino acid substitutions and may influence the substrate specificity of the enzyme. Interestingly, kinetic studies for one of the functional mutants, Asn233Ala, indicate that an alanine substitution at this position significantly increases catalytic efficiency as compared with the wild-type enzyme.

[Indexed for MEDLINE]
Free PMC Article
PubMed Commons home

PubMed Commons


    Supplemental Content

    Full text links

    Icon for Wiley Icon for PubMed Central
    Loading ...
    Support Center