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S. D. McAlear, T. J. Hollingsworth, A. K. Gross; Rhodopsin Autosomal Dominant Retinitis Pigmentosa Mutant Ter349Glu Activates the Phototransduction Cascade. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1673.
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A read-through mutation of rhodopsin, Ter349Glu, leads to one of the most severe forms of Autosomal Dominant Retinitis Pigmentosa (ADRP) observed in a family with a rhodopsin mutation. This mutation results in the addition of 51 amino acids to the rhodopsin C terminus. To begin to understand the role of the mutant protein in the disease pathophysiology, we have tested for abnormal folding and altered signaling of Ter349Glu rhodopsin to the G-protein transducin.
Membranes from COS cells transfected with Ter349Glu or wild type opsin were purified, reconstituted with 11-cis retinal and solubilized. UV/Visible absorbance spectra were measured in the dark and after exposure to light. The ability of the photoactivated rhodopsins to activate the G-protein transducin was monitored by measuring the binding of [35S]GTPγS.
When 11-cis retinal is bound to Ter349Glu opsin, the difference absorbance maximum is 500 nm, the same as wild type rhodopsin. In addition, Ter349Glu rhodopsin activates transducin with an efficiency similar to that of wild type rhodopsin.
The absorbance maximum of 500 nm in the mutant protein indicates that the retinal-binding pocket has not been perturbed in Ter349Glu rhodopsin, implying proper folding. Additionally, in vitro, the addition of the 51 amino acids to the C-terminus of Ter349Glu rhodopsin does not affect the ability of the receptor to activate the phototransduction cascade.
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