title: Structural characterization of a zinc high-affinity binding site in rhodopsin.
abstract: For the first time to our knowledge, X-ray absorption spectroscopy (XAS) has been used to investigate the environment of putative Zn(2+) binding sites in rhodopsin. We studied native purified nondeionized rhodopsin without any further addition of Zn(2+), as well as with 1.5 mol of Zn(2+)-as zinc chloride-per mole of protein. Three different binding sites in rhodopsin were considered based on computational chemistry studies, and a quantitative analysis of the XAS signal was performed by fitting the experimental data to their simulated XAS spectra. Our results demonstrate that Zn(2+) is intrinsically bound to rhodopsin and are compatible with the existence of an octahedral coordination involving six oxygen atoms in the first shell (average Zn-O distance of 2.08 A), and with a second coordination shell containing one or two phosphorus or sulfur atoms at an average distance of 2.81 A.
authors.affiliation: Departament d'Enginyeria Química, Universitat Politècnica de Catalunya, Barcelona, Spain.
authors.forename: Darwin
authors.initials: D
authors.lastname: Toledo
authors.forename: Arnau
authors.initials: A
authors.lastname: Cordomí
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Proietti
authors.forename: Maurizio
authors.initials: M
authors.lastname: Benfatto
authors.forename: Luis J
authors.initials: LJ
authors.lastname: del Valle
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Pérez
authors.forename: Pere
authors.initials: P
authors.lastname: Garriga
authors.forename: Francesc
authors.initials: F
authors.lastname: Sepulcre
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D012243:Rhodopsin / Q000737:chemistry* / Q000378:metabolism*; D013057:Spectrum Analysis; D013379:Substrate Specificity; D015032:Zinc / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D012243:Rhodopsin; D015032:Zinc