Absorbance spectra were recorded at various times after photolysis of hypotonically washed membrane suspensions of human and bovine rhodopsin (pH 7 or 8, T = 20 or 37°C). Global data analysis showed that at 20°C, metarhodopsin III formation was the only process occurring from 1 to 30 min following photolysis. At pH 8, a significant amount of human metarhodopsin I was present before metarhodopsin III formed. At 37°C, two decay processes were seen, formation of metarhodopsin III (lifetime 113 ± 3 sec bovine, 93 ± 2 sec human) and formation of a species with the properties of n-retinylidine opsin (lifetime 900 ± 150 sec bovine, 2000 ± 350 sec human). A larger fraction of human rhodopsin (~ 50%) is converted to metarhodopsin III than is the case for bovine rhodopsin (~ 35%).
Bibliographical noteFunding Information:
The authors wish to thank the Montana Eye Bank for its continued effort to make human eyes available for these studies. We also thank the National Institutes of Health for Grant EY-00983 to DSK. FJGMvK was supported by Grant EY-08818 from the National Eye Institute and by the Air Force Office of Scientific Research, Air Force Systems Command, USAF, under Grant No. 93-NL036. The U.S. government is authorized to reproduce and distribute reprints for governmental purposes notwithstanding any copyright notation hereon. This research was also in part supported by a Research to Prevent Blindness unrestricted grant.
- Dark adaptation
- Human rhodopsin
- Metarhodopsin III
- Retinol dehydrogenase