Structural specificity for the inhibitory effect of calmodulin on specific 125I-omega-conotoxin GVIA binding.
To clear the structural specificity of calmodulin (CaM) on the specific 125I-omega-CTX binding to crude membranes from whole chick brain, the following experiments were investigated in this study: (i) the attenuating effect of semisynthetic tetrahydroisoquinoline derivatives on the inhibitory effect of Ca2+/CaM, (ii) the effects of chimeras of yeast and chicken Ca2+/CaM, and (iii) the effects of Ca2+-binding proteins (such as troponin c, S 100 a and b, and annexin I, III-V). The inhibitory effect of Ca2+/CaM was attenuated by isoquinoline derivatives (PX 28, 34, 216, 224, and CPU57) and a CaM antagonist W-7. PX 34, a typical synthesized isoquinoline derivative, showed the attenuating effect in a dose-dependent manner. The ED50 value for the attenuating effect of PX 34 was about 20 microM, which is similar to that of W-7 reported previously. Some chimeric CaMs such as YC 51-53 (which are close to the properties of vertebrate CaM) showed a significant inhibitory effect on the specific 125I-omega-CTX binding, but YC 129 and 130 (which retain the properties of yeast CaM), troponin c, S100 a, b, and annexin I, III-V had no effect on the specific 125I-omega-CTX binding. These results suggest that the characteristic structure containing the EF-hand structure of CaM itself is needed to cause the inhibitory effect on the specific 125I-omega-CTX binding.
Ichida
Seiji
S
Department of Biological Chemistry, School of Pharmaceutical Sciences, Kinki University, Higashi-Osaka, Japan. seiji@phar.kindai.ac.jp
Abe
Junichi
J
Yu-an
Zhang
Z
Minami
Takeshi
T
Wada
Tetsuyuki
T
Yazawa
Michio
M
Sohma
Hitoshi
H
D000818:Animals; D002147:Calmodulin / Q000494:pharmacology*; D002645:Chickens; D007457:Iodine Radioisotopes; D011869:Radioligand Assay; D020866:omega-Conotoxin GVIA / Q000378:metabolism*
D002147:Calmodulin; D007457:Iodine Radioisotopes; D020866:omega-Conotoxin GVIA