May 1997
Volume 38, Issue 6
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Articles  |   May 1997
Mutation of a conserved cysteine in the X-linked cone opsins causes color vision deficiencies by disrupting protein folding and stability.
Author Affiliations
  • M A Kazmi
    Department of Pediatrics, New York University Medical Center, New York 10016, USA.
  • T P Sakmar
    Department of Pediatrics, New York University Medical Center, New York 10016, USA.
  • H Ostrer
    Department of Pediatrics, New York University Medical Center, New York 10016, USA.
Investigative Ophthalmology & Visual Science May 1997, Vol.38, 1074-1081. doi:
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    • Get Citation

      M A Kazmi, T P Sakmar, H Ostrer; Mutation of a conserved cysteine in the X-linked cone opsins causes color vision deficiencies by disrupting protein folding and stability.. Invest. Ophthalmol. Vis. Sci. 1997;38(6):1074-1081.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

PURPOSE: To test the effects of disruption of a conserved cysteine in the green cone opsin molecule on light-activated isomerization, transducin activation, folding, transport, and protein half-life. METHODS: Stable cell lines were established by transfecting 293-EBNA cells with a plasmid containing wild-type or mutant (C203R, C203S, C126S, C126S/C203S) green opsin cDNA molecules. The proteins were induced by culturing the cells in the presence of cadmium chloride and analyzed by spectra, transducin activation, Western blotting, pulse-labeling with immunoprecipitation, and immunocytochemistry. RESULTS: The C203R mutation disrupts the folding and half-life of the green opsin molecule and its abilities to absorb light at the appropriate wavelength and to activate transducin. Similar disruption of folding, half-life, and light activation occurs when Cys203 or its presumed partner for formation of a disulfide bond (Cys126) is replaced by serine residues. CONCLUSIONS: Like rhodopsin, the folding of the cone opsins appears to be dependent on the formation of a disulfide bond between the third transmembrane helix and the second extracellular loop. Disruption of this disulfide bond represents a cause of color vision deficiencies that is unrelated to spectral shifts of the photopigment.

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