The effect of phosphorylation of gizzard myosin on actin activation |
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Authors: | A Górecka MO Aksoy DJ Hartshorne |
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Institution: | 1. Nencki Institute of Experimental Biology, 3, Pasteur Str. Warsaw, 02-093 Poland;2. Department of Biological Sciences Carnegie-Mellon University, Pittsburgh, Pa. 15213 USA;3. Department of Chemistry Carnegie-Mellon University, Pittsburgh, Pa. 15213 USA |
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Abstract: | Gizzard myosin is phosphorylated by a kinase found in chicken gizzards. The 20,000 dalton light chains are the only subunits to show an appreciable extent of 32P incorporation. Phosphorylation requires trace amounts of Ca2+. The Mg2+-ATPase activity of gizzard myosin in the phosphorylated form is activated to an appreciable extent by skeletal actin, whereas the activation of the non-phosphorylated myosin is verylow. These results suggest that the Ca2+-sensitive regulatory mechanism of gizzard actomyosin is mediated via a kinase. In the presence of Ca2+ the onset of contraction and the resultant increase of the Mg2+-ATPase activity we suggest is due, at least partly, to the phosphorylation of the 20,000 dalton light chains. Whether or not Ca2+ binding by myosin is also essential remains to be established. |
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