Different functional forms of G-protein beta gamma-subunits, beta gamma-I and beta gamma-II, in bovine brain.
Heterotrimeric GTP binding regulatory proteins (G proteins) are involved in the signal transduction process in cells. We have previously demonstrated that G protein (Gi/o) in bovine brain contains two subspecies of the beta gamma-subunit, beta gamma-I and beta gamma-II, with distinct gamma subunits, i.e., gamma-I and gamma-II, but identical beta-subunit. We found that gamma-I agreed with the gamma-subunit reported elsewhere, while gamma-II was a novel gamma-subunit. In the present study we separated the fractions containing G-protein isoforms, Go*, Gi1, Go and Gi2, with a Mono Q column and they were subjected to 15% polyacrylamide gel electrophoresis. All isoforms were shown to possess both gamma subunits, gamma-I and gamma-II. The molar ratio of the two gamma-subunit isoforms was one to one, based on the relative intensity of Coomassie blue-stained bands. Differences in biological activity between G proteins composed of beta gamma-I and beta gamma-II were investigated. The amount of GTP gamma S bound to the alpha-subunit was larger in alpha beta gamma-I than in alpha beta gamma-II. The pertussis toxin-catalyzed ADP-ribosylation on alpha-subunit was enhanced by either beta gamma-subunit subspecies, but the effect was larger with beta gamma-I than with beta gamma-II. From gel filtration with a Sephacryl S 300, it appeared that all alpha- and either beta gamma-subunit, i.e., beta gamma-I or beta gamma-II, formed a trimer complex. These findings suggest the possible existence of two different functional forms in each G-protein isoform depending on the beta gamma-subunit subspecies.
Department of Biochemistry, Sapporo Medical College, Japan.
H
H
Sohma
H
H
Hashimoto
N
N
Hiraike
H
H
Ohguro
T
T
Akino
D000818:Animals; D001923:Brain Chemistry; D002417:Cattle; D019204:GTP-Binding Proteins / Q000737:chemistry*; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D037342:Pertussis Toxin; D011956:Receptors, Cell Surface / Q000737:chemistry; D043562:Receptors, G-Protein-Coupled; D010566:Virulence Factors, Bordetella; D054380:Receptors, CXCR5
D019204:GTP-Binding Proteins; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D037342:Pertussis Toxin; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D010566:Virulence Factors, Bordetella; C513179:CXCR5 protein, mouse; D054380:Receptors, CXCR5