title: Electric fields at the active site of an enzyme: direct comparison of experiment with theory.
abstract: The electric fields produced in folded proteins influence nearly every aspect of protein function. We present a vibrational spectroscopy technique that measures changes in electric field at a specific site of a protein as shifts in frequency (Stark shifts) of a calibrated nitrile vibration. A nitrile-containing inhibitor is used to deliver a unique probe vibration to the active site of human aldose reductase, and the response of the nitrile stretch frequency is measured for a series of mutations in the enzyme active site. These shifts yield quantitative information on electric fields that can be directly compared with electrostatics calculations. We show that extensive molecular dynamics simulations and ensemble averaging are required to reproduce the observed changes in field.
authors.affiliation: Department of Chemistry, Stanford University, Stanford, CA 94305-5080, USA.
authors.forename: Ian T
authors.initials: IT
authors.lastname: Suydam
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Snow
authors.forename: Vijay S
authors.initials: VS
authors.lastname: Pande
authors.forename: Steven G
authors.initials: SG
authors.lastname: Boxer
mesh_terms: D000449:Aldehyde Reductase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D002942:Circular Dichroism; D003198:Computer Simulation; D004560:Electricity; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D008958:Models, Molecular; D009154:Mutation; D009570:Nitriles / Q000378:metabolism / Q000494:pharmacology; D011487:Protein Conformation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D013055:Spectrophotometry, Infrared; D013057:Spectrum Analysis; D055672:Static Electricity
chemical_list: D004791:Enzyme Inhibitors; C512007:IDD743; D009570:Nitriles; C484670:AKR1B1 protein, human; D000449:Aldehyde Reductase