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Substrate specificities in class A β-lactamases: Preference for penams vs. cephams. The role of residues 237

Healey, William J. and Labgold, Marc R. and Richards, John H. (1989) Substrate specificities in class A β-lactamases: Preference for penams vs. cephams. The role of residues 237. Proteins, 6 (3). pp. 275-283. ISSN 0887-3585 . http://resolver.caltech.edu/CaltechAUTHORS:20150430-075008534

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Abstract

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.


Item Type:Article
Related URLs:
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http://dx.doi.org/10.1002/prot.340060310DOIArticle
http://onlinelibrary.wiley.com/doi/10.1002/prot.340060310/abstractPublisherArticle
Additional Information:© 1989 Alan R. Liss, Inc. Received May 15, 1989; revision accepted June 29, 1989. Article first published online: 3 Feb 2004. Ve would like to thank David M. Long for his assistance in the computer modeling and structure generation. This research was supported by NIH Grant GM16424.
Funders:
Funding AgencyGrant Number
NIHGM16424
Subject Keywords:mutagenesis, structure-function relationships, enzymatic catalysis
Record Number:CaltechAUTHORS:20150430-075008534
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20150430-075008534
Official Citation:Healey, W. J., Labgold, M. R. and Richards, J. H. (1989), Substrate specificities in class A β-lactamases: Preference for penams vs. cephams. The role of residues 237. Proteins, 6: 275–283. doi: 10.1002/prot.340060310
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:57101
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:30 Apr 2015 20:35
Last Modified:30 Apr 2015 20:35

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