Ca^<2+> REGULATION OF SMOOTH MUSCLE AONTRACTILE PROTEINS

概要

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By a new method, natural actomyosin (AM) which had Ca^<2+> sensitivity on superprecipitation (SP) and on ATPase activity were extracted from the smooth muscle of various organs. The AM required more Mg^<2+> than skeletal muscle AM for full activation. Sr^<2+> can substitute Ca^<2+> for its activation. Repeated washing of the AM with 2mM KCl and 1mM NaHCO_3 resulted in the loss of its Ca^<2+> sensitivity (desensitized actomyosin (DAM)). On addition of native tropomyosin (NTM) to the DAM, it regained its original Ca^<2+> sensitivity. NTM from the smooth muscle of one visceral organ conferred Ca^<2+> sensitivity to DAM of all other organs. The maximum extent of SP of resensitized AM depended on the activity of NTM rather than the source of AM. NTM from skeletal muscle effectively recovered Ca^<2+> sensitivity of smooth muscle DAM. Therefore, it can be concluded that skeletal muscle NTM works as an activator for smooth msucle with Ca^<2+> and as a depressor in skeletal muscle without Ca^<2+>. α-actinin-like protein extracted from smooth muscle enhanced the activity of DAM-NTM complex. From NTM of smooth muscle, Ca^<2+> regulating protein (CRP) and tropomyosin were isolated and purified. Neither CRP nor TM conferred Ca^<2+> sensitivity to DAM of smooth muscle. But when both proteins were added together, the Ca^<2+> sensitivity of DAM was recovered on SP and ATPase activity.
名古屋市立大学の論文
1978-08-28