Structural Characterization of a Zinc High‐affinity Binding Site in Rhodopsin† |
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| Authors: | Darwin Toledo Arnau Cordomí Maria Grazia Proietti Maurizio Benfatto Luis J Del Valle Juan J Pérez Pere Garriga Francesc Sepulcre |
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| Institution: | 1. Departament d’Enginyeria Química, Universitat Politècnica de Catalunya, Barcelona, Spain;2. Centre de Biotecnologia Molecular (CEBIM), Universitat Politècnica de Catalunya, Barcelona, Spain;3. These two authors contributed equally to this work.;4. Departamento de Física de la Materia Condensada, ICMA, CSIC‐Universidad de Zaragoza, Zaragoza, Spain;5. Lab. Nazionali di Frascati‐INFN‐PO, Frascati, Italy;6. Departament d’Enginyeria Agroalimentària i Biotecnologia, Universitat Politècnica de Catalunya, Castelldefels, Spain |
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| Abstract: | For the first time to our knowledge, X‐ray absorption spectroscopy (XAS) has been used to investigate the environment of putative Zn2+ binding sites in rhodopsin. We studied native purified nondeionized rhodopsin without any further addition of Zn2+, as well as with 1.5 mol of Zn2+—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 Zn2+ 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. |
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