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PMID: 19760664 Published · ppublish English Journal Article Research Support, N.I.H., Extramural

Trp fluorescence reveals an activation-dependent cation-pi interaction in the Switch II region of Galphai proteins.

Protein science : a publication of the Protein Society ·Vol. 18 ·No. 11 ·2009-11-00 ·Pages 2326-35

Hamm HE, Meier SM, Liao G, Preininger AM

Abstract

Crystal structures of Galpha(i) (and closely related family member Galpha(t)) reveal much of what we currently know about G protein structure, including changes which occur in Switch regions. Galpha(t) exhibits a low rate of basal (uncatalyzed) nucleotide exchange and an ordered Switch II region in the GDP-bound state, unlike Galpha(i), which exhibits higher basal exchange and a disordered Switch II region in Galpha(i)GDP structures. Using purified Galpha(i) and Galpha(t), we examined the intrinsic tryptophan fluorescence of these proteins, which reports conformational changes associated with activation and deactivation of Galpha proteins. In addition to the expected enhancement in tryptophan fluorescence intensity, activation of GalphaGDP proteins was accompanied by a modest but notable red shift in tryptophan emission maxima. We identified a cation-pi interaction between tryptophan and arginine residues in the Switch II of Galpha(i) family proteins that mediates the observed red shift in emission maxima. Furthermore, amino-terminal myristoylation of Galpha(i) resulted in a less polar environment for tryptophan residues in the GTPase domain, consistent with an interaction between the myristoylated amino terminus and the GTPase domain of Galpha proteins. These results reveal unique insights into conformational changes which occur upon activation and deactivation of G proteins in solution.

MeSH Terms
Arginine/metabolism GTP-Binding Protein alpha Subunits, Gi-Go/chemistry,genetics,metabolism Guanosine 5'-O-(3-Thiotriphosphate)/metabolism Guanosine Diphosphate/metabolism Kinetics Models, Molecular Myristic Acid/metabolism Protein Conformation Protein Structure, Tertiary/genetics Spectrometry, Fluorescence/methods Tryptophan/metabolism
Chemicals
Myristic Acid Guanosine Diphosphate Guanosine 5'-O-(3-Thiotriphosphate) Tryptophan Arginine GTP-Binding Protein alpha Subunits, Gi-Go
Authors & Affiliations
4 authors, click to expand affiliations / ORCID
Hamm Heidi E
Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA.
Meier Scott M
Liao Guihua
Preininger Anita M
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Article Info
Journal
Protein science : a publication of the Protein Society
Abbr.
Protein Sci
ISSN
1469-896X
DOI
10.1002/pro.243
Published
2009-11-00
Pages
2326-35
Language
English
Region
United States
NLM ID
9211750
PMCID
PMC2788287
Subset
IM
Grants
NEI NIH HHS · EY06062 · United States
NCRR NIH HHS · P41 RR-01081 · United States
External Links
PubMed source DOI: 10.1002/pro.243 PMC Full Text View journal details
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