March 2012
Volume 53, Issue 14
ARVO Annual Meeting Abstract  |   March 2012
Rhodopsin Photolysis in Mouse Disk Membranes After Targeted Deletion of Transducin β-Complex
Author Affiliations & Notes
  • Oleg G. Kisselev
    Ophthalmology, Saint Louis University Eye Institute, St Louis, Missouri
  • Elena Lomonosova
    Ophthalmology, Saint Louis University Eye Institute, St Louis, Missouri
  • Alexander V. Kolesnikov
    Ophthalmology, Washington University, St Louis, Missouri
  • Vladimir J. Kefalov
    Ophthalmology & Visual Sciences, Washington University School of Medicine, Saint Louis, Missouri
  • Footnotes
    Commercial Relationships  Oleg G. Kisselev, None; Elena Lomonosova, None; Alexander V. Kolesnikov, None; Vladimir J. Kefalov, None
  • Footnotes
    Support  NIH grants RO1GM63203, R21EY018107 (OGK), EY019312 and EY02112601 (VJK).
Investigative Ophthalmology & Visual Science March 2012, Vol.53, 4136. doi:
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      Oleg G. Kisselev, Elena Lomonosova, Alexander V. Kolesnikov, Vladimir J. Kefalov; Rhodopsin Photolysis in Mouse Disk Membranes After Targeted Deletion of Transducin β-Complex. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4136.

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

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Purpose: : The focus of the present study is to characterize the possible role of transducin (Gt) βγ-complex in modulating the signaling properties of photoactivated rhodopsin and its lifetime in rod disk membranes and intact rods using Gtγ-deficient mice.

Methods: : We studied rhodopsin photolysis using UV-Visible spectroscopy and rapid scanning spectroscopy in the presence of hydroxylamine in highly purified wild type and Gtγ-deficient mouse rod disk membranes. Complex formation between photoactivated rhodopsin and transducin was measured by spectroscopic assay of extra-Metarhodopsin II formation at 5% rhodopsin bleach levels. Recovery of dark current and flash sensitivity following a moderate 12% rhodopsin bleach in individual intact wild type and Gtγ-deficient mouse rods was measured by single-cell suction recordings.

Results: : Photoconversion of rhodopsin to Meta I/Meta II equilibrium proceeds normally after the elimination of transducin βγ-complex in mouse rod disk membranes. The Meta I/Meta II ratio, the rate of Meta II decay, the reactivity of Meta II toward hydroxylamine, and the rate of Meta III formation in Gtγ-deficient rod disk membranes were identical to those observed in wild type samples. The lack of Gtβγ did not affect the stability of dark-state rhodopsin in the presence of hydroxylamine. Under low intensity illumination, the amount of extra-Meta II in Gtγ-deficient discs was significantly reduced. The initial rate of dark current recovery following 12% rhodopsin bleach was 3 times faster in Gtγ-deficient rods, while the rate of the late current recovery was largely unchanged. Mutant rods also exhibited faster postbleach recovery of their flash sensitivity.

Conclusions: : Photoactivation and thermal decay of rhodopsin proceed similarly in wild type and Gtγ-deficient mouse rods, but the complex formation between photoactivated rhodopsin and transducin is severely compromised in the absence of Gtβγ. The resulting lower transduction activation contributes to faster photoresponse recovery following a moderate pigment bleach in Gtγ-deficient rods.

Keywords: photoreceptors • protein structure/function • electrophysiology: non-clinical 

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