Event Title
Exploring How the N152T Mutation in the Class C ²-lactamase, AmpC, can Serve as a Substrate Selectivity Switch
Presentation Type
Poster/Portfolio
Presenter Major(s)
Chemistry
Mentor Information
Brad Wallar
Department
Chemistry
Location
Henry Hall Atrium 25
Start Date
10-4-2013 12:00 PM
End Date
10-4-2013 1:00 PM
Keywords
Health, Life Science
Abstract
AmpC is a main cause of antibiotic resistance in some types of bacteria. While some active site residues' catalytic roles have been revealed, their contributions to which antibiotic they can inactivate is unknown. Prior work has shown that a mutation of a highly conserved residue in the active site (N152) can result in substrate selectivity changes in similar class C beta-lactamases. The role of the active site residue asparagine-152 (N152) mutated to threonine (T) allowed us to examine the kinetic and structural properties of this mutant with beta-lactam antibiotics. Although the N152T mutation caused a higher Km with all substrates, N152T exhibits over 150 fold higher kcat against cefotaxime. To investigate the mechanism of the observed change in selectivity, the X-ray crystal structure of AmpC N125T was determined. In comparison to the wild type AmpC structure, small structural active site differences have been associated with the changes in the kinetic values.
Exploring How the N152T Mutation in the Class C ²-lactamase, AmpC, can Serve as a Substrate Selectivity Switch
Henry Hall Atrium 25
AmpC is a main cause of antibiotic resistance in some types of bacteria. While some active site residues' catalytic roles have been revealed, their contributions to which antibiotic they can inactivate is unknown. Prior work has shown that a mutation of a highly conserved residue in the active site (N152) can result in substrate selectivity changes in similar class C beta-lactamases. The role of the active site residue asparagine-152 (N152) mutated to threonine (T) allowed us to examine the kinetic and structural properties of this mutant with beta-lactam antibiotics. Although the N152T mutation caused a higher Km with all substrates, N152T exhibits over 150 fold higher kcat against cefotaxime. To investigate the mechanism of the observed change in selectivity, the X-ray crystal structure of AmpC N125T was determined. In comparison to the wild type AmpC structure, small structural active site differences have been associated with the changes in the kinetic values.