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January 1, 1991Protein Engineering Design and Selection

Arginine 220 is a critical residue for the catalytic mechanism of the Streptomyces albus G β-lactamase

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Authors

FJFrançoise Jacob‐DubuissonCentre National de la Recherche ScientifiqueJLJosette Lamotte‐BrasseurUniversity of LiègeODO. DidebergCentre National de la Recherche Scientifique

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Implication

Mutational analysis reveals critical role of Arg220 in Streptomyces albus G beta-lactamase acylation, highlighting structural mechanisms of substrate carboxylate recognition.

Key Points

  • Investigate the catalytic and structural role of residue Arg220 in substrate recognition and acylation by Streptomyces albus G beta-lactamase.
  • Engineered an R220L site-directed mutant of the Streptomyces albus G class A beta-lactamase.
  • Assayed kinetic efficiency (kcat/Km) and acylation rates against classical beta-lactams, neutral esters, cephaloridine, and cephalothin.
  • Conducted molecular modeling of enzyme-substrate complexes to assess active-site charge interactions.
  • The R220L substitution markedly decreased kcat/Km values for penicillins and cephalosporins carrying C3/C4 carboxylates, but minimally altered acylation by neutral substrates like benzylpenicillin methylester.
  • Enzyme activity was preserved substantially more against cephaloridine than cephalothin, indicating substrate-assisted catalysis where a substrate-borne positive charge compensates for the absent arginine.
  • Comparative structural modeling revealed that Arg220 functionally matches Arg244 in other class A beta-lactamases by positioning a guanidinium group to interact with the substrate carboxylate.

Cite This Study

Jacob‐Dubuisson et al. (1991) studied this question.

synapsesocial.com/papers/6a70bc3b6ceb2bbd16dffb4ahttps://doi.org/10.1093/protein/4.7.811
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