title: Crystallographic studies on the complex behavior of nicotine binding to P450cam (CYP101).
abstract: Crystallographic and spectroscopic studies have been undertaken to characterize the binding behavior of the non-native substrate nicotine in the active site of the monooxygenase hemoprotein cytochrome P450cam. Despite the existence of a theoretical model that is consistent with the observed distribution of monooxygenation products, the crystal structure of the complex indicates that the primary binding mode of nicotine is unproductive. The structure is confirmed by spectral data that indicate direct coordination of substrate pyridine nitrogen with the heme iron. This would be the proper structure for evaluating binding affinity and inhibition. Reduction of the heme from Fe(III) to Fe(II) and introduction of carbon monoxide into crystals of the nicotine-P450cam complex, to simulate molecular oxygen binding, produces reorientation of the nicotine. This orientation is the appropriate one for predicting regioselectivity and the kinetic features of substrate oxidation. While it is not clear that such complicated behavior will be exhibited for other enzyme-substrate interactions, it is clear that a single crystal structure for a given substrate-enzyme interaction may not provide a good description of the binding mode responsible for product formation.
authors.affiliation: Department of Biophysics, University of Rochester, Rochester, New York 14627, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Strickler
authors.forename: Barry M
authors.initials: BM
authors.lastname: Goldstein
authors.forename: Kathleen
authors.initials: K
authors.lastname: Maxfield
authors.forename: Laura
authors.initials: L
authors.lastname: Shireman
authors.forename: Gyungyoun
authors.initials: G
authors.lastname: Kim
authors.forename: Donald S
authors.initials: DS
authors.lastname: Matteson
authors.forename: Jeffrey P
authors.initials: JP
authors.lastname: Jones
mesh_terms: D001665:Binding Sites; D019475:Camphor 5-Monooxygenase / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D002248:Carbon Monoxide / Q000737:chemistry / Q000378:metabolism; D003198:Computer Simulation; D003460:Crystallization; D018360:Crystallography, X-Ray; D008956:Models, Chemical; D008958:Models, Molecular; D009538:Nicotine / Q000737:chemistry* / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D013053:Spectrophotometry; D013379:Substrate Specificity
chemical_list: D011994:Recombinant Proteins; D009538:Nicotine; D002248:Carbon Monoxide; D019475:Camphor 5-Monooxygenase