Relationship between specific binding of 125I-omega-conotoxin GVIA and GTP binding protein: effects of the GTP analogues, mastoparan and A1F4-.
We investigated whether the specific binding or labeling of 125I-omega-CgTX on crude membranes from chick whole brain was affected when endogenous GTP binding protein (G protein) was activated by GTP analogues, mastoparan (MP) and aluminum fluoride (AIF4-; AICl3 + NaF). Both GTPgammaS and Gpp(NH)p attenuated the inhibitory effect of selective N-type Ca channel inhibitors such as aminoglycoside antibiotics (AGs) or dynorphine (1-13)(Dyn) on specific 125I-omega-CgTX binding in a dose-dependent manner. On the other hand, the inhibitory effects of the divalent metal cations Cd2+, Co2+, Mg2+ and Mn2- on such binding were not attenuated by GTPgammaS. MP and AIF4- also attenuated the inhibitory effect of Neo on this binding similar to GTPgammaS. The attenuating effect of MP was enhanced by the presence of Mg2+ in a dose-dependent manner. However, GTP analogues, MP and AIF4-, did not affect binding or labeling without AGs or Dyn. GTPgammaS, MP and AIF4- also attenuated the specific labeling of a 215-kDa band in crude membranes with 125I-omega-CgTX using the cross-linker DSS (non-reduced condition) in the presence of Neo. These results indicate that there are direct or indirect relationships between N-type Ca channels and G proteins via binding sites for AGs or MP.
Ichida
S
S
Department of Biological Chemistry, Faculty of Pharmaceutical Sciences, Kinki University, Higashi-Osaka, Japan. seiji@phar.kindai.ac.jp
Wada
T
T
Tahara
M
M
Imoto
K
K
Zhang
Y A
YA
D017607:Aluminum Compounds / Q000494:pharmacology*; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D002645:Chickens; D005459:Fluorides / Q000494:pharmacology*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives*; D036341:Intercellular Signaling Peptides and Proteins; D007457:Iodine Radioisotopes; D010455:Peptides / Q000378:metabolism*; D014862:Wasp Venoms / Q000494:pharmacology*; D020866:omega-Conotoxin GVIA
D017607:Aluminum Compounds; D036341:Intercellular Signaling Peptides and Proteins; D007457:Iodine Radioisotopes; D010455:Peptides; D014862:Wasp Venoms; C050992:tetrafluoroaluminate; C037500:mastoparan; D006160:Guanosine Triphosphate; D020866:omega-Conotoxin GVIA; D019204:GTP-Binding Proteins; D005459:Fluorides