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Primary events in dim light vision: a chemical and spectroscopic approach toward understanding protein/chromophore interactions in rhodopsin
Author(s) -
Fishkin Nathan,
Berova Nina,
Nakanishi Koji
Publication year - 2004
Publication title -
the chemical record
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.61
H-Index - 78
eISSN - 1528-0691
pISSN - 1527-8999
DOI - 10.1002/tcr.20000
Subject(s) - rhodopsin , chromophore , biophysics , chemistry , neuroscience , biology , photochemistry , retinal , biochemistry
The visual pigment rhodopsin (bovine) is a 40 kDa protein consisting of 348 amino acids, and is a prototypical member of the subfamily A of G protein‐coupled receptors (GPCRs). This remarkably efficient light‐activated protein (quantum yield = 0.67) binds the chromophore 11‐ cis ‐retinal covalently by attachment to Lys296 through a protonated Schiff base. The 11‐ cis geometry of the retinylidene chromophore keeps the partially active opsin protein locked in its inactive state (inverse agonist). Several retinal analogs with defined configurations and stereochemistry have been incorporated into the apoprotein to give rhodopsin analogs. These incorporation results along with the spectroscopic properties of the rhodopsin analogs clarify the mode of entry of the chromophore into the apoprotein and the biologically relevant conformation of the chromophore in the rhodopsin binding site. In addition, difference UV, CD, and photoaffinity labeling studies with a 3‐diazo‐4‐oxo analog of 11‐ cis ‐retinal have been used to chart the movement of the retinylidene chromophore through the various intermediate stages of visual transduction. © 2004 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 4: 120–135; 2004: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.20000