A blue-light-activated GTP-binding protein in the plasma membranes of etiolated peas.
Heterotrimeric GTP-binding regulatory proteins (G proteins) have been identified as part of signal transduction systems in a wide variety of organisms. In this paper, we establish the presence of a G protein associated with the plasma membranes of the apical bud of etiolated peas. The GTPase activity is induced by low fluences of blue light administered to plasma membrane-enriched fractions. The activity is not responsive to red-light irradiation and is specific for GTP. The threshold for the excitation of the GTPase activity in vitro is less than 10(-1) mumol.m-2 of blue light, consistent with participation in the blue low-fluence system identified in the same tissue. A 40-kDa polypeptide is recognized by polyclonal antisera directed against the alpha subunit of the G protein transducin. The polypeptide also serves as a substrate for ADP-ribosylation by cholera and pertussis toxins. The ability of the 40-kDa polypeptide to serve as substrate for the toxin-mediated ribosylation is mediated by blue-light irradiation, implying that the 40-kDa polypeptide is the alpha subunit of a blue-light-stimulated G protein. The 40-kDa polypeptide binds a nonhydrolyzable photoaffinity-labeling analog of GTP only after irradiation with blue light. The protein we have described may function as an alpha subunit of a G protein active in the process of light-mediated development in higher plants.
Warpeha
K M
KM
Department of Biological Sciences, University of Illinois, Chicago 60680.
Hamm
H E
HE
Rasenick
M M
MM
Kaufman
L S
LS
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002772:Cholera Toxin / Q000494:pharmacology; D003429:Cross Reactions; D003624:Darkness; D007887:Fabaceae / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000302:isolation & purification / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism* / Q000528:radiation effects; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D007700:Kinetics; D008027:Light; D008970:Molecular Weight; D009243:NAD / Q000378:metabolism; D037342:Pertussis Toxin; D010946:Plants, Medicinal; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D010566:Virulence Factors, Bordetella; D009243:NAD; D000246:Adenosine Diphosphate Ribose; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D002772:Cholera Toxin; D037342:Pertussis Toxin; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins