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Structural Characterization of a Zinc High‐affinity Binding Site in Rhodopsin †
Author(s) -
Toledo Darwin,
Cordomí Arnau,
Proietti Maria Grazia,
Benfatto Maurizio,
Del Valle Luis J.,
Pérez Juan J.,
Garriga Pere,
Sepulcre Francesc
Publication year - 2009
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.2008.00529.x
Subject(s) - rhodopsin , x ray absorption spectroscopy , zinc , chemistry , absorption spectroscopy , crystallography , spectroscopy , coordination number , octahedron , inorganic chemistry , crystal structure , ion , biochemistry , physics , optics , retinal , organic chemistry , quantum mechanics
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 Å), and with a second coordination shell containing one or two phosphorus or sulfur atoms at an average distance of 2.81 Å.