The sequence of the gene for beta-lactamase I from Bacillus cereus 569/H has been redetermined. Oligonucleotide-directed mutagenesis has been carried out, and the effects of the changes on the ampicillin-resistance of Escherichia coli TG1 expressing the mutant genes have been studied. Lysine-73, close to the active-site serine-70 and a highly-conserved residue, has been converted into arginine. This change had a large effect on activity, but did not abolish it. An even larger effect was found in the mutant in which glutamate-166 had been converted into glutamine; this had little or no activity. On the other hand, the conversion of glutamate-168 into aspartate gave fully active enzyme. Glutamate-166 is an invariant residue, but glutamate-168 is not. Alanine-123 has been replaced by cysteine, to give active enzyme; this change forms part of the plan to introduce a disulphide bond into the enzyme.
Research Article|December 15 1987
β-lactamase I from Bacillus cereus. Structure and site-directed mutagenesis
P J Madgwick;
Biochem J (1987) 248 (3): 657-662.
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P J Madgwick, S G Waley; β-lactamase I from Bacillus cereus. Structure and site-directed mutagenesis. Biochem J 15 December 1987; 248 (3): 657–662. doi: https://doi.org/10.1042/bj2480657
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