Structural characterization of a zinc high-affinity binding site in rhodopsin.
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.
Toledo
Darwin
D
Departament d'Enginyeria Química, Universitat Politècnica de Catalunya, Barcelona, Spain.
Cordomí
Arnau
A
Proietti
Maria Grazia
MG
Benfatto
Maurizio
M
del Valle
Luis J
LJ
Pérez
Juan J
JJ
Garriga
Pere
P
Sepulcre
Francesc
F
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*
D012243:Rhodopsin; D015032:Zinc