Yamamoto K, Nunoi K, Fujishima M
Health Services Center, Kyushu Institute of Design, Fukuoka, Japan.
J Mol Cell Cardiol. 1990 Mar;22(3):279-85. doi: 10.1016/0022-2828(90)91461-f.
In an effort to clarify the regulation of contractions in cardiac muscle, we performed ultracentrifugation studies on the interactions between cardiac troponin and tropomyosin-actin complex in the presence of Ca2+ or Sr2+. When troponin C and troponin I were centrifuged with tropomyosin-actin complex, troponin I was not removed from tropomyosin-actin complex in the presence of bivalent-cation. Troponin C was observed to bind very weakly to troponin T-tropomyosin-actin complex in either the presence of absence of bivalent-cation. When troponin C was replaced by calmodulin, troponin I was not removed from tropomyosin-actin complex in the presence of bivalent-cation. Calmodulin bound to the troponin I-troponin T-tropomyosin-actin complex only in the presence of bivalent-cation. These results suggest that the inhibitory action of troponin I is neutralized by troponin C or calmodulin upon binding of bivalent-cation while troponin I binds to tropomyosin-actin complex in cardiac muscle. Therefore cardiac muscle seems to differ from skeletal muscle in regard to regulation of its contraction.
为了阐明心肌收缩的调节机制，我们进行了超速离心研究，以探讨在存在Ca2+或Sr2+的情况下心肌肌钙蛋白与原肌球蛋白 - 肌动蛋白复合物之间的相互作用。当肌钙蛋白C和肌钙蛋白I与原肌球蛋白 - 肌动蛋白复合物一起离心时，在二价阳离子存在的情况下，肌钙蛋白I不会从原肌球蛋白 - 肌动蛋白复合物中去除。无论是否存在二价阳离子，都观察到肌钙蛋白C与肌钙蛋白T - 原肌球蛋白 - 肌动蛋白复合物的结合非常弱。当用钙调蛋白取代肌钙蛋白C时，在二价阳离子存在的情况下，肌钙蛋白I不会从原肌球蛋白 - 肌动蛋白复合物中去除。钙调蛋白仅在二价阳离子存在时与肌钙蛋白I - 肌钙蛋白T - 原肌球蛋白 - 肌动蛋白复合物结合。这些结果表明，在二价阳离子结合时，肌钙蛋白I的抑制作用被肌钙蛋白C或钙调蛋白中和，而肌钙蛋白I在心肌中与原肌球蛋白 - 肌动蛋白复合物结合。因此，心肌在收缩调节方面似乎与骨骼肌不同。
