In an effort to elucidate the mechanism of calmodulin regulation of muscle contraction, we investigated the interaction between calmodulin and troponin components in the presence of Ca2+ or Sr2+ by the use of ultracentrifugation methods and polyacrylamide-gel electrophoresis. Skeletal-muscle troponin C bound to troponin I and dissociated it from the tropomyosin-actin complex in the presence of Ca2+ or Sr2+. When troponin T was absent, calmodulin bound to troponin I and dissociated it from the tropomyosin-actin complex in the presence of Ca2+ or Sr2+. When troponin T was present, calmodulin hardly bound to troponin I even in the presence of bivalent cations. Trifluoperazine, a calmodulin antagonist, inhibited the bivalent-cation-dependent interaction between calmodulin and troponin I. Calmodulin migrated more slowly in the presence of Sr2+ than it did in the presence of EGTA but faster than it did in the presence of Ca2+ on polyacrylamide-gel electrophoresis under non-denaturing conditions. It is concluded that troponin T is not required in the calmodulin regulation of muscle contraction because troponin T inhibits the bivalent-cation-dependent interaction between calmodulin and troponin I and because calmodulin binds to troponin I and dissociates it from the tropomyosin-actin complex in a bivalent-cation-dependent manner. Sr2+-induced exposure of the hydrophobic region enables calmodulin to bind to troponin I, as is the case with Ca2+.
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February 1987
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Research Article|
February 01 1987
Interaction of calmodulin with troponin I and the troponin-tropomyosin-actin complex. Effect of Ca2+ and Sr2+ ions
Publisher: Portland Press Ltd
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 1987 London: The Biochemical Society
1987
Biochem J (1987) 241 (3): 905–909.
Citation
K Yamamoto, H Nakayama, K Nunoi, M Fujishima; Interaction of calmodulin with troponin I and the troponin-tropomyosin-actin complex. Effect of Ca2+ and Sr2+ ions. Biochem J 1 February 1987; 241 (3): 905–909. doi: https://doi.org/10.1042/bj2410905
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