Characteristics of the inhibitory effect of calmodulin on specific [125i]omega-conotoxin GVIA binding to crude membranes from chick brain.
The characteristics of the inhibitory effect of calcium ion (Ca2+)/calmodulin (CaM) on specific [125I]-omega-conotoxin GVIA (125I-omega-CTX) binding and on the labeling of 125I-omega-CTX to crude membranes from chick brain were investigated. The inhibitory effect of Ca2+/CaM depended on the concentrations of free Ca2+ and CaM. The IC50 values for free Ca2+ and CaM were about 2.0 x 10(-8) M and 3.0 microg protein/ml, respectively. The inhibitory effect of Ca2+/CaM was attenuated by the CaM antagonists W-7, prenylamine and CaM-kinase II fragment (290-309), but not by the calcineurin inhibitor FK506. Ca2+/CaM also inhibited the labeling of a 135-kDa band (which was considered to be part of N-type Ca2+ channel alpha1 subunits) with 125I-omega-CTX using a cross-linker. These results suggest that Ca2+/CaM affects specific 125I-omega-CTX binding sites, probably N-type Ca2+ channel alpha1 subunits, in crude membranes from chick whole brain.
Ichida
S
S
Department of Biological Chemistry, Faculty of Pharmaceutical Sciences, Kinki University, Higashi-Osaka, Japan.
Abe
J
J
Zhang
Y A
YA
Sugihara
K
K
Imoto
K
K
Wada
T
T
Fujita
N
N
Sohma
H
H
D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000378:metabolism*; D020864:Calcium Channels, N-Type / Q000187:drug effects / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000494:pharmacology; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002645:Chickens; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007457:Iodine Radioisotopes; D007527:Isoenzymes / Q000494:pharmacology; D008297:Male; D008566:Membranes / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology; D011299:Prenylamine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013449:Sulfonamides / Q000494:pharmacology; D020866:omega-Conotoxin GVIA / Q000037:antagonists & inhibitors*
D002121:Calcium Channel Blockers; D020864:Calcium Channels, N-Type; D002147:Calmodulin; D004791:Enzyme Inhibitors; D007457:Iodine Radioisotopes; D007527:Isoenzymes; D010446:Peptide Fragments; D013449:Sulfonamides; C017967:W 7; D020866:omega-Conotoxin GVIA; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D011299:Prenylamine; D002118:Calcium