Journal article
Binding of Transducin to Light-Activated Rhodopsin Prevents Transducin Interaction with the Rod cGMP Phosphodiesterase γ-Subunit
Biochemistry (Easton), Vol.36(14), pp.4188-4193
04/08/1997
DOI: 10.1021/bi963002y
PMID: 9100013
Abstract
In photoreceptor cells of vertebrates, the GTP-bound α-subunit of rod G-protein, transducin (Gt α), interacts with the cGMP phosphodiesterase inhibitory γ-subunit (Pγ) to activate the effector enzyme. The GDP-bound Gt α can also bind the Pγ subunit, albeit with a lower affinity than Gt αGTP. In this work, interactions between Gt αGDP and Pγ or Pγ-24−45Cys labeled with the fluorescent probe 3-(bromoacetyl)-7-(diethylamino)coumarin (PγBC, Pγ-24−45BC) have been investigated. Addition of Gt αGDP to PγBC produced approximately a 6-fold maximal increase in the probe fluorescence, while the fluorescence of Pγ-24−45BC was enhanced by 2.3-fold. The K d's for the Gt αGDP binding to PγBC and Pγ-24−45BC were 75 ± 8 nM and 400 ± 110 nM, respectively. The Gt βγ subunits had no notable effect on the binding of Gt αGDP to PγBC or Pγ-24−45BC, suggesting that Pγ and Gt βγ bind to Gt αGDP noncompetitively. The Gt αβγ interaction with the fluorescently labeled Pγ was effectively blocked in the light-activated rhodopsin (R*)−Gt αβγ complex. Furthermore, addition of excess Pγ or Pγ-24−45 prevented binding of Gt αβγ to R*, indicating that the R* and Pγ binding surfaces on Gt αβγ may overlap. It is likely that R* has a binding site within the α3−β5 region of Gt α, which is a proposed site of Gt αGDP binding to Pγ-24−45. Alternatively, R* may induce conformational changes of the Gt α α3−β5 region such that the resulting structural changes alter the adjacent consensus sequence for the guanine ring binding of GDP/GTP(NKXD), and lead to a reduction in the affinity of G-protein for guanine nucleotides.
Details
- Title: Subtitle
- Binding of Transducin to Light-Activated Rhodopsin Prevents Transducin Interaction with the Rod cGMP Phosphodiesterase γ-Subunit
- Creators
- Nikolai O Artemyev
- Resource Type
- Journal article
- Publication Details
- Biochemistry (Easton), Vol.36(14), pp.4188-4193
- Publisher
- American Chemical Society
- DOI
- 10.1021/bi963002y
- PMID
- 9100013
- ISSN
- 0006-2960
- eISSN
- 1520-4995
- Language
- English
- Date published
- 04/08/1997
- Academic Unit
- Molecular Physiology and Biophysics; Iowa Neuroscience Institute; Ophthalmology and Visual Sciences
- Record Identifier
- 9984025683402771
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