Chromophore structural changes in rhodopsin from nanoseconds to microseconds following pigment photolysis

摘要

Rhodopsin is a prototypical G protein- coupled receptor that is activated by photoisomerization of its 11-cis-retinal chromophore. Mutant forms of rhodopsin were prepared in which the carboxylic acid counterion was moved relative to the positively charged chromophore Schiff base. Nanosecond time-resolved laser photolysis measurements of wild-type recombinant rhodopsin and two mutant pigments then were used to determine reaction schemes and spectra of their early photolysis intermediates. These results, together with linear dichroism data, yielded detailed structural infor- mation concerning chromophore movements during the first microsecond after photolysis.