Hozumi T
Department of Physiology, Nagoya City University Medical School, Japan.
Biochem Int. 1991 Mar;23(5):835-43.
As is well known, the ATPase/structural interactions between the S-1 moieties of myosin molecules ("cross bridges") and actin molecules in polymerized ("F") form are thought to underlie muscle contraction. It is surmised that such interactions are unitary (1 S-1:1 actin), but actual demonstration thereof is handicapped by intrinsic properties of the proteins. It is known that monomeric ("G" form) actin binds to S-1 and that in this contact only the 633-642 region of S-1 is involved; however, such unions do not activate S-1 ATPase. Recently, Bettache et al. (1989) [Proc. Natl. Acad. Sci. USA 86, 6028-6032] showed that chemically modified actin can be kept in monomeric form, and makes a stable unitary complex with S-1, but without activating S-1 ATPase. In this paper, however, we show that when such complexes are covalently crosslinked by 1-ethyl-3-[3-(dimethylamino)-propyl]carbodiimide they recover activated ATPase. The existence of such activated complexes proves an excellent model system as a soluble analogue of the F-actin-(S-1) complex.
众所周知，肌球蛋白分子的S-1部分（“横桥”）与聚合形式（“F”型）的肌动蛋白分子之间的ATP酶/结构相互作用被认为是肌肉收缩的基础。据推测，这种相互作用是单一的（1个S-1：1个肌动蛋白），但其实际证明受到蛋白质固有特性的阻碍。已知单体形式（“G”型）的肌动蛋白与S-1结合，并且在这种接触中仅涉及S-1的633-642区域；然而，这种结合不会激活S-1 ATP酶。最近，贝塔切等人（1989年）[《美国国家科学院院刊》86，6028 - 6032]表明，化学修饰的肌动蛋白可以保持单体形式，并与S-1形成稳定的单一复合物，但不会激活S-1 ATP酶。然而，在本文中，我们表明当这种复合物通过1-乙基-3-[3-(二甲基氨基)丙基]碳二亚胺进行共价交联时，它们会恢复激活的ATP酶活性。这种激活复合物的存在证明了一个极好的模型系统，可作为F-肌动蛋白-（S-1）复合物的可溶性类似物。
