Direct activation of GTP-binding proteins by venom peptides that contain cationic clusters within their alpha-helical structures.
Direct interactions of venom peptides that contained a cysteine-stabilized alpha-helical motif within their internal molecules with alpha beta gamma-trimeric GTP-binding proteins (G proteins) were studied in reconstituted phospholipid vesicles. Mast cell-degranulating (MCD) peptide stimulated the steady-state rate of GTP hydrolysis catalyzed by the reconstituted G proteins. Synthetic D-MCD peptide, the optical isomer of MCD peptide, was also effective in the activation of G proteins as L-MCD peptide. The stimulations by L- and D-peptides were both abolished in G proteins that had been ADP-ribosylated by pertussis toxin. Charybdotoxin also stimulated, though slightly, the GTPase activity of G proteins. Such a stimulation was, however, not observed upon the incubation of G proteins with other venom peptides such as apamin, sarafotoxin and endothelin. Thus, in comparison of the amino acid sequences of their venom peptides, the extent of the activation of G proteins appeared to be correlated with the number of basic amino acid residues around the alpha-helix. These results suggest that cationic clusters at one side of the alpha-helical surface are more important in the direct activation of G proteins than a specific, alpha-helical structure.
Tomita
U
U
Department of Life Science, Tokyo Institute of Technology, Yokohama, Japan.
Takahashi
K
K
Ikenaka
K
K
Kondo
T
T
Fujimoto
I
I
Aimoto
S
S
Mikoshiba
K
K
Ui
M
M
Katada
T
T
D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D008081:Liposomes; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000494:pharmacology*; D037342:Pertussis Toxin; D011487:Protein Conformation; D012689:Sequence Homology, Nucleic Acid; D014688:Venoms / Q000737:chemistry*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D008081:Liposomes; D010455:Peptides; D014688:Venoms; D010566:Virulence Factors, Bordetella; D037342:Pertussis Toxin; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins