Characterization of heterotrimeric G protein complexes in rice plasma membrane.
Two genes in the rice genome were identified as those encoding the gamma subunits, gamma1 and gamma2, of heterotrimeric G proteins. Using antibodies against the recombinant proteins for the alpha, beta, gamma1, and gamma2 subunits of the G protein complexes, all of the subunits were proven to be localized in the plasma membrane in rice. Gel filtration of solubilized plasma membrane proteins showed that all of the alpha subunits were present in large protein complexes (about 400 kDa) containing the other subunits, beta, gamma1, and gamma2, and probably also some other proteins, whereas large amounts of the beta and gamma (gamma1 and gamma2) subunits were freed from the large complexes and took a 60-kDa form. A yeast two-hybrid assay and co-immunoprecipitation experiments showed that the beta subunit interacted tightly with the gamma1 and gamma2 subunits, and so the beta and gamma subunits appeared to form dimers in rice cells. Some dimers were associated with the alpha subunit, because few beta, gamma1, and gamma2 subunits were present in the 400-kDa complexes in a rice mutant, d1, which was lacking in the alpha subunit. When a constitutively active form of the alpha subunit was prepared by the exchange of one amino acid residue and introduced into d1, the mutagenized subunit was localized in the plasma membrane of the transformants and took a free, and not the 400-kDa, form.
Kato
Chiyuki
C
Department of Bioscience, Fukui Prefectural University, 4-1-1 Kenjyojima, Matsuoka-cho, Yoshida-gun, Fukui 910-1195, Japan.
Mizutani
Tomohiro
T
Tamaki
Hisanori
H
Kumagai
Hidehiko
H
Kamiya
Takehiro
T
Hirobe
Ayumi
A
Fujisawa
Yukiko
Y
Kato
Hisaharu
H
Iwasaki
Yukimoto
Y
D000595:Amino Acid Sequence; D001483:Base Sequence; D002462:Cell Membrane / Q000378:metabolism; D003429:Cross Reactions; D018076:DNA, Complementary / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D017343:Genes, Plant; D020962:Heterotrimeric GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D012275:Oryza / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012995:Solubility; D020798:Two-Hybrid System Techniques
D018076:DNA, Complementary; D018744:DNA, Plant; D046911:Macromolecular Substances; D008565:Membrane Proteins; D010940:Plant Proteins; D021122:Protein Subunits; D011994:Recombinant Proteins; D020962:Heterotrimeric GTP-Binding Proteins