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  • 1
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 3 (1975), S. 125-140 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The reactivity of myosin to [14C]-labeled N-ethylmaleimide ([14C] NEM) or to tritium was determined in functionally different frog muscles. The incorporation of [14C] NEM into myosin decreased during isotonic or isometric contractions, as compared to resting muscle. The cysteine residues which were protected during contraction were not involved in the ATPase activity or the actin-binding ability of myosin. Peptide mapping revealed that several residues were protected simultaneously. The incorporation of tritium into the peptide N-H groups of myosin was also decreased during muscle activity. These data support the idea that activation and subsequent contraction of muscle are correlated with structural changes in the myosin molecule.The reactivity of myosin to [14C] NEM was increased when the muscle was stretched to 140% rest length and treated with iodoacetate to deplete ATP. Based on in vitro experiments and on literature data, it is suggested that in the resting muscle myosin contains bound MgATP which decreases the rate of incorporation of [14C] NEM into myosin and that upon the irreversible loss of ATP the rate increases.31P nuclear magnetic resonance signals from a number of phosphates were detected in the intact frog muscle. The data indicated that the minimum concentration of ATP in the muscle is 3 mM, a value which agrees with that of chemical determination. The characteristic chemical shifts, coupling constants, and line widths of ATP in the muscle were considerably altered from that of either free ATP in aqueous solutions or ATP in perchloric acid extracts of muscle.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Electrophoresis 4 (1983), S. 138-142 
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The phosphorylatable light chain of myosin (P-light chain) from hearts of the turtle, rat, frog, dog, cat, adult chicken and 1 week old chick was compared by two dimensional gel electrophoresis. The technique separates the phospho and dephospho forms of P-light chain and allows quantitation of its percentage distribution. The P-light chain was found to exist in multiple forms. The turtle heart possessed the highest percentage, 75%, of the phospho form of P-light chain, whereas 25% of P-light chain was in the dephospho form. In rat heart, 35% of the P-light chain was phosphorylated and 65% dephosphorylated. In frog heart, the P-light chain exhibited three forms: two phosphorylated and one dephosphorylated. The P-light chain of dog, cat and adult chicken hearts displayed four spots on two-dimensional gel electrophoresis: two phospho and two dephospho forms. In these species the percentage of total P-light chain being in the phospho forms was in the range of 10-25%. Comparison of adult chicken and 1 week old chick preparations suggests that during maturation from the chick to the chicken the percentage phospho form of the total P-light chain decreases. The myosin light chain kinase and phosphatase activities in whole homogenates of the above heart preparations were assayed. The data, with the exception of those from frog heart, suggest that the extent of light chain phosphorylation is correlated with the ratio of light chain kinase to phosphatase activity.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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