Combinatorial biochemistry and shuffling of TEM, SHV and Streptomyces albus omega loops in PSE-4 class A β-lactamase

The class A PSE-4 β-lactamase was used for studying the importance of amino acids in the omega (Ω) loop and its interactions for hydrolysis of β-lactam antibiotics. By cassette mutagenesis, we replaced the amino acids 163-179 Ω loop in PSE-4 with TEM-1, SHV-1 and Streptomyces albus G β-lactamase Ω loops. Phenotypic analysis of Escherichia coli recombinants expressing the Ω loop PSE-4 mutant enzymes gave MICs and kinetic data similar to those of wild-type PSE-4.