Chemistry Commons^™

Mechanism Of Rate-Limiting Motions In Enzyme Function, Eric D. Watt, Hiroko Shimada, Evgueni Kovriguine, J. Patrick Loria

Chemistry Faculty Research and Publications

The ability to use conformational flexibility is a hallmark of enzyme function. Here we show that protein motions and catalytic activity in a RNase are coupled and display identical solvent isotope effects. Solution NMR relaxation experiments identify a cluster of residues, some distant from the active site, that are integral to this motion. These studies implicate a single residue, histidine-48, as the key modulator in coupling protein motion with enzyme function. Mutation of H48 to alanine results in loss of protein motion in the isotope-sensitive region of the enzyme. In addition, k _cat decreases for this mutant and the kinetic …