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(Circulation. 1961;24:390.)
© 1961 American Heart Association, Inc.

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The ATPases of Muscle Proteins

John V. Taggart M.D.; MANUEL F. MORALES PH.D.¹; SHIZUO WATANABE SC.D.¹

¹ From the Cardiovascular Research Institute, University of California Medical School, San Francisco, California.

The ideas and results of Blum, Oosawa, Strohman, and many others are reviewed and, when consolidated with the authors' work, lead to the following picture of muscle protein adenosine triphosphatases (ATPases). Two major features of myocin ATPase seem to be a catalytic interaction between enzyme, a metal cation, and the terminal pyrophosphate moiety of adenosine triphosphate (ATP) and a rate-retarding interaction between enzyme, Mg⁺⁺, and the purine ring of ATP. Sulfhydryl groups of the enzyme participate at both loci. In the catalytic interaction an ionizable group (pK, ca. 6.8) may participate. G-actin molecules binding ATP (probably by the purine ring) and relieved of their mutual repulsion cooperate in catalysing dephosphorylation, thereby giving rise to the somewhat loose, possibly helical, structure of F-actin.