Two forms of intermediates of frog rhodopsin in rod outer segments.
Using frog rod outer segments, we measured changes of the absorption spectrum during the conversion of rhodopsin to a photosteady-state mixture composed of rhodopsin, isorhodopsin and bathorhodopsin by irradiation with blue light (440 nm) at -190 degrees C and during the reversion of bathorhodopsin to a mixture of rhodopsin and isorhodopsin by irradiation with red light (718 nm) at -190 degrees C. The reaction kinetics was expressed by one exponential in the former case and by two exponentials in the latter. These results suggest that rhodopsin is composed of a single molecular species, while bathorhodopsin is composed of two kinds of molecular species designated as batho1-rhodopsin and batho2-rhodopsin. On warming the two forms of bathorhodopsin, each bathorhodopsin converted to its own lumirhodopsin, metarhodopsin I and finally a free all-trans-retinal plus opsin. The absorption spectra of the two forms of bathorhodopsin, lumirhodopsin and metarhodopsin I were measured at -190 degrees C. We infer that a rhodopsin molecule in the excited state relaxes to either batho1-rhodopsin or batho2-rhodopsin, and then converts to its own intermediates through one of the two parallel pathways.
D000818:Animals; D007700:Kinetics; D008027:Light; D010786:Photoreceptor Cells / Q000378:metabolism*; D011892:Rana catesbeiana; D012168:Retinal Pigments / Q000378:metabolism*; D012243:Rhodopsin / Q000031:analogs & derivatives / Q000378:metabolism*; D012374:Rod Cell Outer Segment / Q000378:metabolism*; D013053:Spectrophotometry
D012168:Retinal Pigments; C013110:metarhodopsins; C015017:bathorhodopsin; D012243:Rhodopsin