A point mutation uncouples transducin-alpha from the photoreceptor RGS and effector proteins

Michael Natochin; Nikolai O Artemyev

doi:10.1046/j.1471-4159.2003.02103.x

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A point mutation uncouples transducin-alpha from the photoreceptor RGS and effector proteins

Journal article

Open access

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A point mutation uncouples transducin-alpha from the photoreceptor RGS and effector proteins

Michael Natochin and Nikolai O Artemyev

Journal of neurochemistry, Vol.87(5), pp.1262-1271

12/2003

DOI: 10.1046/j.1471-4159.2003.02103.x

PMID: 14622106

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Abstract

A novel gain-of-function mutation, R243Q, has been recently identified in the Candida elegans Gqalpha protein EGL-30. The position corresponding to Arg243 in EGL-30 is absolutely conserved among heterotrimeric G proteins. This mutation appears to be the first gain-of-function mutation in the switch III region of Galpha subunits. To investigate consequences of the R-->Q mutation we introduced the corresponding R238Q mutation into transducin-like Gtalpha* subunit. The mutant retained intact interactions with Gtbetagamma and rhodopsin but exhibited a twofold reduction in the kcat value for guanosine 5'-triphosphate (GTP) hydrolysis. The GTPase activity of R238Q was not accelerated by the RGS domain of the visual GTPase-activating protein, RGS9-1. In addition, R238Q displayed a significant impairment in the effector function. Our data and the crystal structures of transducin suggest that the major reason for the reduced intrinsic GTPase activity of R238Q and the lack of RGS9 function is the break of the conserved ionic contact between Arg238 and Glu39, which apparently stabilizes the transitional state for GTP hydrolysis. We hypothesize that the R243Q mutation in EGL-30 severs the ionic interaction of Arg243 with Glu43, leading to a defective inactivation of the mutant by the C. elegans RGS protein EAT-16.

Fungal Proteins - chemistry

Amino Acid Sequence

GTP-Binding Protein alpha Subunits, Gq-G11 - genetics

Transducin - genetics

Protein Binding - genetics

Mutagenesis, Site-Directed

Molecular Sequence Data

Structure-Activity Relationship

Fungal Proteins - genetics

Rhodopsin - metabolism

Transducin - chemistry

Protein Folding

Point Mutation

Candida

RGS Proteins - chemistry

Conserved Sequence

RGS Proteins - metabolism

Transducin - metabolism

Guanosine Triphosphate - chemistry

Enzyme Activation - genetics

Fungal Proteins - metabolism

Rhodopsin - chemistry

Details

Title: Subtitle: A point mutation uncouples transducin-alpha from the photoreceptor RGS and effector proteins
Creators: Michael Natochin - Department of Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, IA 52242, USA
Nikolai O Artemyev
Resource Type: Journal article
Publication Details: Journal of neurochemistry, Vol.87(5), pp.1262-1271
Publisher: England
DOI: 10.1046/j.1471-4159.2003.02103.x
PMID: 14622106
ISSN: 0022-3042
eISSN: 1471-4159
Grant note: R01 EY 12682 / NEI NIH HHS
Language: English
Date published: 12/2003
Academic Unit: Molecular Physiology and Biophysics; Iowa Neuroscience Institute; Ophthalmology and Visual Sciences
Record Identifier: 9984025360702771

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