Direct interactions of mastoparan and compound 48/80 with GTP-binding proteins.
The effects of mastoparan and compound 48/80 on the activities of alpha beta gamma-trimeric GTP-binding proteins (G proteins) were studied with purified Go and Gi-1 which had been reconstituted into phospholipid vesicles. Pertussis toxin-catalyzed ADP-ribosylation of Go or Gi-1 was inhibited by mastoparan or compound 48/80, suggesting that the G proteins were dissociated into their constituent alpha- and beta gamma-subunits in the presence of these compounds. The steady-state rate of GTP hydrolysis catalyzed by Go or Gi-1 was stimulated by the two compounds. Both the stimulations were due to increases in the rate of the GDP-GTP exchange reaction occurring on the G proteins. However, the modes stimulation of the GTPase activity depended on the type of G protein used, and the stimulations caused by the two compounds were differently affected by pertussis toxin-catalyzed ADP-ribosylation of G proteins. Moreover, the mastoparan-induced stimulation of the GTPase activity was partially inhibited by compound 48/80. Thus, the two histamine secretagogues mastoparan and compound 48/80 appear to activate G proteins differently, though they interact with the signal-transducing proteins, at least partly, at a common binding site.
Tomita
U
U
Department of Life Science, Tokyo Institute of Technology, Kanagawa.
Inanobe
A
A
Kobayashi
I
I
Takahashi
K
K
Ui
M
M
Katada
T
T
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D020558:GTP Phosphohydrolases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006868:Hydrolysis; D066298:In Vitro Techniques; D036341:Intercellular Signaling Peptides and Proteins; D007700:Kinetics; D008081:Liposomes; D010455:Peptides; D014862:Wasp Venoms / Q000494:pharmacology*; D003189:p-Methoxy-N-methylphenethylamine / Q000494:pharmacology*
D036341:Intercellular Signaling Peptides and Proteins; D008081:Liposomes; D010455:Peptides; D014862:Wasp Venoms; D000246:Adenosine Diphosphate Ribose; D003189:p-Methoxy-N-methylphenethylamine; C037500:mastoparan; D006160:Guanosine Triphosphate; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins