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Evidence suggested there might exist in brain a contractile protein: 1) actomyosin contains Nacetyl aspartic acid; brain contains a high concentration of the free compound, 2) actomyosin functions as a Mg dependent ATPase; brain contains a Mg dependent ATPase, 3) actomyosin-like contractile proteins have been described in cells, membranes, and tissues other than muscle. Therefore whole rat brains were extracted with 0.6M KCl and the extract diluted to O.lM KCl. The precipitate exhibited superprecipitation (SP) properties which required both Mg and ATP. SP was inhibited by p-chloro-mercuribenzene sulfonic acid (10- M) but not by ouabain (10 M). The protein purified by reprecipitation hydrolyzed 7xl0-3 μMoles ATP/min/mg protein; the ATPase activity was completely inhibited by 10-3 Mersalyl but only partially by 10-4M ouabain (20%). This protein represents about 1% of the total brain protein. Experiments with 1-14C-acetate suggested the presence in brain of acetate covalently bound to protein. The contractile protein appears to account for at least part of the Mg dependent ATPase activity of brain

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Federation proceedings. 27 no. 464:page 1392

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