Characterization of the transition state of functional enzyme dynamics.
Through characterization of the solvent isotope effect on protein dynamics, we have examined determinants of the rate limitation to enzyme catalysis. A global conformational change in Ribonuclease A limits the overall rate of catalytic turnover. Here we show that this motion is sensitive to solvent deuterium content; the isotope effect is 2.2, a value equivalent to the isotope effect on the catalytic rate constant. We further demonstrate that the protein motion possesses a linear proton inventory plot, indicating that a single proton is transferred in the transition state. These results provide compelling evidence for close coupling between enzyme dynamics and function and demonstrate that characterization of the transition state for protein motion in atomic detail is experimentally accessible.
Kovrigin
Evgenii L
EL
Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520, USA.
Loria
J Patrick
JP
D017666:Deuterium Oxide / Q000737:chemistry*; D004795:Enzyme Stability; D006860:Hydrogen Bonding; D007700:Kinetics; D011487:Protein Conformation; D017510:Protein Folding; D012259:Ribonuclease, Pancreatic / Q000737:chemistry* / Q000378:metabolism*
D012259:Ribonuclease, Pancreatic; D017666:Deuterium Oxide