LIGHT INDUCED INTERACTION BETWEEN RHODOPSIN AND GTP DEPENDENT PROCESSES IN ROD OUTER SEGMENTS—I. KINETIC ANALYSES OF LIGHT SCATTERING TRANSIENTS |
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| Authors: | B D Gupta S Deshpande † R E Jones T J Borys E W Abrahamson ‡; |
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| Institution: | Department of Chemistry and Biochemistry, University of Guelph, Guelph, Ontario N1G 2W1, Canada |
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| Abstract: | Abstract— A fast light-induced light scattering transient in the presence of Mg2+ and GTP is observed from bovine rod outer segment suspension. This transient is studied at various temperatures, degrees of photo-bleaching and GTP concentration. The kinetic analysis of this signal at low photo-bleaching (～ 5%) reveals two different processes which are consecutive rather than simultaneous. The rate of both processes depends upon the extent of photo-bleaching and indicates that each process requires a photolyzed rhodopsin intermediate. At low temperature, the rate constant of both the processes increases with the extent of photo-bleaching while at higher temperatures it decreases. The calculated activation energy of both processes decreases with increasing photo-bleaching. It has also been observed that with decreasing GTP concentration, the rates of both processes decrease indicating that the two processes though first order are most likely bimolecular, first order in both GTP and the photolytic rhodopsin intermediate (metarhodopsin II) |
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