PURIFICATION AND LOW-TEMPERATURE SPECTROSCOPY OF GECKO VISUAL PIGMENTS GREEN AND BLUE

We purified two kinds of visual pigments, gecko green and gecko blue, from retinas of Tokay geckos (Gekko gekko) by two steps of column chro matography, and investigated their photobleaching processes by means o f low temperature spectroscopy. Absorption maxima of gecko green and b lue solubilized in a mixture of holamidopropyl)dimethylammonio]-1-prop anesulfonate (CHAPS) and phosphatidylcholine were 522 and 465 nm, resp ectively, which are close to those observed in the photoreceptor cells . Low temperature spectroscopy identified six intermediates in the pho tobleaching process of gecko green; batho (lambda(max) = 569 nm), BL ( gamma(max) = 519 nm), lumi (507 nm), meta I (similar to 486 nm), meta II (similar to 384 nm), and meta HI intermediates (similar to 500 nm). In contrast to the high similarity in amino acid sequence between gec ko green and iodopsin [Kojima, D., et al. (1992) Proc. Natl. Acad. Sci . U.S.A. 89, 6841-6845], the batho-green did not revert thermally to o riginal gecko green but converts to the next intermediate. The photobl eaching process of gecko blue was investigated by low temperature spec troscopy, and three intermediates, meta I (gamma(max) = similar to 470 nm), meta II (gamma(max) similar to 370 nm) and meta III (gamma(max) similar to 475 nm), were identified. A comparative study on the therma l behavior of meta intermediates revealed that the thermal stability o f meta II intermediate of both of the gecko visual pigments is lower t han that of metarhodopsin II. The result supports the idea that both t he gecko visual pigments are cone-type ones.