Difference absorption spectra were recorded during the formation and decay of metarhodopsin III after sonicated membrane suspensions of rhodopsin were bleached at 37°C. The data were analyzed using SVD, spectral decomposition and global exponential fitting. By comparison of the results in the presence or absence of 70 μM NADPH and those for bovine or human rhodopsin, a single comprehensive scheme was fit to all the data, including reduction of retinal to retinol by the intrinsic retinol dehydrogenase. On the time scale studied the mechanism involves two 382 nm absorbing species and two 468 nm, absorbing species, supporting the notion that human metarhodopsin III is not a homogeneous species. The results confirm that metarhodopsin III forms and persists sufficiently long in the human retina under physiological conditions that it could undergo secondary photoisomerization. Copyright (C) 2000 Elsevier Science Ltd.
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 the Air Force Office of Scientific Research, Air Force Systems Command, USAF, under Grant No. 93-NLO36. The US 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.
Copyright 2017 Elsevier B.V., All rights reserved.
- Dark adaptation
- Human rhodopsin
- Metarhodopsin III
- Retinol dehydrogenase