[Molecular mechanisms of photoreception. IV. Photoregeneration of rhodopsin from metarhodopsin II using the artificial lipid membrane method for detection of intermediate steps of this reaction].

It was shown that photoregeneration of rhodopsin from metarhodopsin II takes place in bovine retinal rod outer segment disc membrane fragments. Photoregenerated rhodopsin is identical to unbleached rhodopsin in spectra and in stability to NH2OH. Moreover, as an unbleached pigment, photoregenerated rhodopsin can induce the transient increase of the artificial lipid membrane (ALM) conductivity in response to visible light. It was shown, that the UV-light converts metarhodopsin II to rhodopsin through the new long-lived (tau approximately 5 min) intermediate product (X500). X500 is indistinguishable from rhodopsin spectrophotometrically, but it can not induce the transient increase of ALM conductivity in response to visible light. It was shown that P467 (this product is obtained usually by photolysis of metarhodopsin II) has a retinal chromophore in all-trans configuration. This result indicates that P467 is produced from cis-metarhodopsin II and X500 (these products are the intermediates of the back reaction metarhodopsin II--rhodopsin) but not from metarhodopsin II as suggested earlier. A modified scheme of the back reaction metarhodopsin II--rhodopsin is given.