Rhodopsin Recognition by Mutant Gsα Containing C-terminal Residues of Transducin
| Autor: | Randall L. McEntaffer, Nikolai O. Artemyev, Michael Natochin, Khakim G. Muradov |
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| Rok vydání: | 2000 |
| Předmět: |
Models
Molecular Rhodopsin Gs alpha subunit G protein Stereochemistry Recombinant Fusion Proteins GTP-Binding Protein alpha Subunits Glycine Glutamic Acid Alpha (ethology) Biology Guanosine Diphosphate Biochemistry Heterotrimeric G protein GTP-Binding Protein alpha Subunits Gs Animals Amino Acid Sequence Transducin Molecular Biology Binding Sites C-terminus Cell Biology Mutagenesis Site-Directed biology.protein Cattle Guanosine Triphosphate |
| Zdroj: | Journal of Biological Chemistry. 275:2669-2675 |
| ISSN: | 0021-9258 |
| DOI: | 10.1074/jbc.275.4.2669 |
| Popis: | The C-terminal regions of the heterotrimeric G protein alpha-subunits play key roles in selective activation of G proteins by their cognate receptors. In this study, mutant G(s)alpha proteins with substitutions by C-terminal residues of transducin (G(t)alpha) were analyzed for their interaction with light-activated rhodopsin (R*) to delineate the critical determinants of the G(t)alpha/R* coupling. In contrast to G(s)alpha, a chimeric G(s)alpha/G(t)alpha protein containing only 11 C-terminal residues from transducin was capable of binding to and being potently activated by R*. Our results suggest that Cys(347) and Gly(348) are absolutely essential, whereas Asp(346) is more modestly involved in the G(t) activation by R*. In addition, the analysis of the intrinsic nucleotide exchange in mutant G(s)alpha indicated an interaction between the C terminus and the switch II region in G(t)alpha.GDP. Mutant G(s)alpha containing the G(t)alpha C terminus and substitutions of Asn(239) and Asp(240) (switch II) by the corresponding G(t)alpha residues, Glu(212) and Gly(213), displayed significant reductions in spontaneous guanosine 5'-O-(3-thiotriphosphate)-binding rates to the levels approaching those in G(t)alpha. Communication between the C terminus and switch II of G(t)alpha does not appear essential for the activational coupling between G(t) and R*, but may represent one of the mechanisms by which Galpha subunits control intrinsic nucleotide exchange. |
| Databáze: | OpenAIRE |
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