ISSN:
0887-3585
Keywords:
mutagenesis
;
structure-function relationships
;
enzymatic catalysis
;
Chemistry
;
Biochemistry and Biotechnology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Medicine
Notes:
Site saturation mutagenesis has been carried out at Ala-237 in RTEM-1 β-lactamase to assess the role of this site in modulating differences in specificity of β-lactamases for penams vs. cephams as substrates. (An Ala-237 Thr mutation had previously been shown to increase activity on cephems by about 30-80%.1,2) Screening of all 19 possibles mutants on penams and cephems revealed the even more active Ala-237 Asn mutant. Detailed kinnetic analysis showns that this mutant has about four times the activity toward cephalothin and cephalosporin C as the wild-type enzyme. Both mutations reduce the activity toward penams to about 10% that of RETM-1 β-lactamase and lower by about 5°C the tempreature at which the enzyme denatures. Functional properties of the other mutants have also been surveyed. The most intresting aspect of these results is that two quite disparate amino acids, theronine and asparagine, when intorduced for Ala-237, cause such similar changes in enzyme specificity while more similar residues do not alter the catalytic properties of the enzyme to such a significant degree.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/prot.340060310
