Reconstitution of Troponin Activity from Three Protein Components

Abstract

Pursed troponin prepared according to published procedures was separated into four major protein fractions when chromatographed on DEAE-Sephadex in 6 rd urea.The main components in Fractions 1 to 4 had approximate molecular weights of 14,000,24,000,35,000, and 21,000, respectively, as determined by sodium dodecyl sulfate gel electrophoresis.Reconstitution experiments using all possible combinations indicated that Fractions 2, 3, and 4 restored the Ca+f requirement for the ATPase activity of actomyosin in the presence of tropomyosin.Recovery of activity could only be achieved when the required components were mixed prior to removal of urea.This suggests that one or more of these proteins may refold improperly on removal of urea unless the other components are present.