Journal article
Identification of Effector Residues on Photoreceptor G Protein, Transducin
The Journal of biological chemistry, Vol.273(34), pp.21808-21815
08/21/1998
DOI: 10.1074/jbc.273.34.21808
PMID: 9705319
Abstract
Transducin is a photoreceptor-specific heterotrimeric GTP-binding protein that plays a key role in the vertebrate visual transduction cascade. Here, using scanning site-directed mutagenesis of the chimeric Galphat/Galphai1 alpha-subunit (Galphat/i), we identified Galphat residues critical for interaction with the effector enzyme, rod cGMP phosphodiesterase (PDE). Our evidence suggests that residue Ile208 in the switch II region directly interacts with the effector in the active GTP-bound conformation of Galphat. Residues Arg201, Arg204, and Trp207 are essential for the conformation-dependent Galphat/effector interaction either via direct contacts with the inhibitory PDE gamma-subunit or by forming an effector-competent conformation through the communication network between switch II and the switch III/alpha3-helix domain of Galphat. Residues His244 and Asn247 in the alpha3 helix of Galphat are responsible for the conformation-independent effector-specific interaction. Insertion of these residues rendered the Galphat/i chimera with the ability to bind PDE gamma-subunit and stimulate PDE activity approaching that of native Galphat. Comparative analysis of the interactions of Galphat/i mutants with PDE and RGS16 revealed two adjacent but distinct interfaces on transducin. This indicates a possibility for a functional trimeric complex, RGS/Galpha/effector, that may play a central role in turn-off mechanisms of G protein signaling systems, particularly in phototransduction.
Details
- Title: Subtitle
- Identification of Effector Residues on Photoreceptor G Protein, Transducin
- Creators
- Michael NatochinAlexey E GranovskyNikolai O Artemyev
- Resource Type
- Journal article
- Publication Details
- The Journal of biological chemistry, Vol.273(34), pp.21808-21815
- DOI
- 10.1074/jbc.273.34.21808
- PMID
- 9705319
- NLM abbreviation
- J Biol Chem
- ISSN
- 0021-9258
- eISSN
- 1083-351X
- Language
- English
- Date published
- 08/21/1998
- Academic Unit
- Molecular Physiology and Biophysics; Iowa Neuroscience Institute; Ophthalmology and Visual Sciences
- Record Identifier
- 9984025438302771
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