Identification of a region in G protein gamma subunits conserved across species but hypervariable among subunit isoforms.
The heterotrimeric GTP binding proteins, G proteins, consist of three distinct subunits: alpha, beta, and gamma. There are 12 known mammalian gamma subunit genes whose products are the smallest and most variable of the G protein subunits. Sequencing of the bovine brain gamma(10) protein by electrospray mass spectrometry revealed that it differs from the human protein by an Ala to Val substitution near the N-terminus. Comparison of gamma isoform subunit sequences indicated that they vary substantially more at the N-terminus than at other parts of the protein. Thus, species variation of this region might reflect the lack of conservation of a functionally unimportant part of the protein. Analysis of 38 gamma subunit sequences from four different species shows that the N-terminus of a given gamma subunit isoform is as conserved between different species as any other part of the protein, including highly conserved regions. These data suggest that the N-terminus of gamma is a functionally important part of the protein exhibiting substantial isoform-specific variation.
Cook
L A
LA
Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
Schey
K L
KL
Cleator
J H
JH
Wilcox
M D
MD
Dingus
J
J
Hildebrandt
J D
JD
D000409:Alanine / Q000737:chemistry; D000818:Animals; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D017124:Conserved Sequence; D020224:Expressed Sequence Tags; D020962:Heterotrimeric GTP-Binding Proteins / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D010802:Phylogeny; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D021241:Spectrometry, Mass, Electrospray Ionization; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014633:Valine / Q000737:chemistry
D020033:Protein Isoforms; D020962:Heterotrimeric GTP-Binding Proteins; D014633:Valine; D000409:Alanine