Purchase this article with an account.
A.D. Albert, V, T.C. Edrington, M.P. Bennett; Effect of Opsin on the Thermal Stability of Rhodopsin . Invest. Ophthalmol. Vis. Sci. 2006;47(13):815.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To determine the effect of opsin on the thermal stability of rhodopsin. Rhodopsin is highly concentrated in the plane of the membrane and has been proposed to exist as a dimer or higher order oligomers. In this study we investigate the effect of partial bleaching on the temperature of thermal denaturation (Tm) and the activation energy for thermal denaturation (Eact) of opsin and rhodopsin to determine if opsin contact with rhodopsin alters the stability of rhodopsin.
Disk membranes were exposed to light to achieve between 0 and 100% bleaching. Differential scanning calorimetry experiments were performed using a MicroCal VP–DSC microcalorimeter. Each sample was scanned at a rate of15, 30, 60 and 90o/hr. Because the protein transitions are irreversible, a second scan was used to determine the baseline.
Rhodopsin exhibits considerably greater thermal stability than does opsin. This is reflected in the thermal denaturation temperature, which is almost 20 oC higher for rhodopsin than for opsin. The Tm for rhodopsin and opsin were determined in the same DSC scan. The Tm remained constant for rhodopsin regardless of the level of bleaching while the Tm for opsin did not. The Eact was calculated from the dependence of the protein transition temperature (Tm) on the rate of the increase of temperature (scan rate).
In isolated disk membranes rhodopsin behaves as a monomer or exhibits extraordinary cooperativity with respect to its thermal properties.
This PDF is available to Subscribers Only