Nov 20, 1975

Radioactive labeling and location of specific thiol groups in myosin from fast, slow and cardiac muscles

Biochimica Et Biophysica Acta
M PfisterP G Waser


1. Based on incorporation of radioactively labeled N-ethylmaleimide, the readily reactive thiol groups of isolated myosin (EC from fast, slow and cardiac muscles could be classified into 3 types. All 3 myosins contain 2 thiol-1, 2 thiol-2 and a variable number of thiol-3 groups per molecule. Both thiol-1 and thiol-2 groups which are essential for functioning of the K+-stimulated ATPase, are located in the heavy chains in all 3 myosin types. 2. The variation in the incorporation pattern of N-ethylmaleimide over the 3 thiol group classes under steady-state conditions of Mg(2+) - ATP hydrolysis allowed different conformations of some reaction intermediates to be characterized. In all 3 types of myosin the hydrolytic cycle of Mg(2+) - ATP was found to be controlled by the same step at 25 degrees C. In all three cases, this rate-limiting step is changed in the same way by lowereing temperature. 3. Using the chemically determined molecular weights for myosin light chains, their stoichiometry was found on the basis of sodium dodecyl sulfate electrophoresis to be 1.2 : 2.1 : 0.8 for light chain-1: light chain-2:light chain-3 per molecule of fast myosin, 2.0 : 1.9 for light chain-1:light chain-2 per molecule of slow myosin and ...Continue Reading

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Mentioned in this Paper

Adenosine Triphosphatases
Smooth Muscle
Sulfhydryl Compounds
Plasma Protein Binding Capacity
Chinchilla Rabbits
Protein Conformation

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