title: Crystal structure of the putidaredoxin reductase x putidaredoxin electron transfer complex.
abstract: In the camphor monooxygenase system from Pseudomonas putida, the [2Fe-2S]-containing putidaredoxin (Pdx) shuttles electrons between the NADH-dependent putidaredoxin reductase (Pdr) and cytochrome P450(cam). The mechanism of the Pdr.Pdx redox couple has been investigated by a variety of techniques. One of the exceptions is x-ray crystallography as the native partners associate weakly and resist co-crystallization. Here, we present the 2.6-A x-ray structure of a catalytically active complex between Pdr and Pdx C73S/C85S chemically cross-linked via the Lys(409Pdr)-Glu(72Pdx) pair. The 365 A(2) Pdr-Pdx interface is predominantly hydrophobic with one central Arg(310Pdr)-Asp(38Pdx) salt bridge, likely assisting docking and orienting the partners optimally for electron transfer, and a few peripheral hydrogen bonds. A predicted 12-A-long electron transfer route between FAD and [2Fe-2S] includes flavin flanking Trp(330Pdr) and the iron ligand Cys(39Pdx). The x-ray model agrees well with the experimental and theoretical results and suggests that the linked Pdx must undergo complex movements during turnover to accommodate P450(cam), which could limit the Pdx-to-P450(cam) electron transfer reaction.
authors.affiliation: Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697-3900, USA. sevrioui@uci.edu
authors.forename: Irina F
authors.initials: IF
authors.lastname: Sevrioukova
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Poulos
authors.forename: Inna Y
authors.initials: IY
authors.lastname: Churbanova
mesh_terms: D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D018360:Crystallography, X-Ray; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry* / Q000235:genetics; D045222:Electron Transport Chain Complex Proteins / Q000737:chemistry* / Q000235:genetics; D005288:Ferredoxins / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D020125:Mutation, Missense; D009247:NADH, NADPH Oxidoreductases / Q000737:chemistry* / Q000235:genetics; D020836:Protein Structure, Quaternary; D016958:Pseudomonas putida / Q000201:enzymology* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D045222:Electron Transport Chain Complex Proteins; D005288:Ferredoxins; C100137:putidaredoxin; D003577:Cytochrome P-450 Enzyme System; D009247:NADH, NADPH Oxidoreductases; C022486:putidaredoxin reductase