title: Calcium ion and troponin: Professor S. Ebashi's epoch-making achievement.
abstract: The processes by which Professor Setsuro Ebashi accomplished his great work are described. Independently of Marsh, Ebashi discovered the relaxing factor in homogenized muscle and showed that it has a lipid-containing particulate fraction with ATPase activity, later identified as the sarcoplasmic reticulum. He then solved the mechanism of relaxation of the relaxing factor through the following findings. A minute amount of calcium ion (Ca(2+)) is necessary for the physiological contractile reaction. The relaxing factor strongly accumulates Ca(2+) in the presence of ATP and sufficiently removes Ca(2+) from the contractile system to bring about relaxation. Ebashi found that the contractile reaction of myosin and actin is regulated by Ca(2+) only in the presence of a tropomyosin-like protein factor, which he later showed to be a complex of tropomyosin and a new protein, troponin. He proved that troponin is the Ca(2+)-receptive protein and proposed the correct scheme for the molecular mechanism of regulation of contraction and relaxation.
authors.affiliation: Saitama Medical University, Faculty of Medical Care and Health, Kawagoe 350-1123, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Endo
mesh_terms: D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D049673:History, 20th Century; D007564:Japan; D008954:Models, Biological; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D009482:Neurophysiology / Q000266:history*; D014336:Troponin / Q000502:physiology*
chemical_list: D014336:Troponin; D002118:Calcium