title: The adeonosine-triphosphatase activity of desensitized actomyosin.
abstract: 1. A simple procedure involving repeated washings of actomyosin, extracted as the complex from myofibrils (natural actomyosin) at ionic strength less than 0.002, is described for the preparation of a desensitized actomyosin. 2. The Mg(2+)-activated adenosine triphosphatase of natural actomyosin was markedly inhibited by ethylenedioxybis(ethyleneamino)tetra-acetic acid, whereas that of the desensitized actomyosin was unaffected. 3. The activity of the Ca(2+)-activated adenosine triphosphatase of natural actomyosin was generally lower than that of the Mg(2+)-activated adenosine triphosphatase, whereas in the desensitized actomyosin the difference between the activities was considerably less. In both natural and desensitized actomyosin the adenosine-triphosphatase activities in the presence of Mg(2+) were similar. 4. The conversion of the natural into the desensitized actomyosin was accompanied by the removal of a protein fraction containing the factors responsible for the sensitivity to ethylenedioxybis(ethyleneamino)tetra-acetic acid and for modifying the Ca(2+)-activated adenosine triphosphatase. When added to a desensitized actomyosin this fraction effected a reversal to the natural form. The recombination was facilitated by increasing the ionic strength of the medium. The two factors showed different stabilities to heat and tryptic digestion.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D002122:Calcium Chloride; D002614:Chelating Agents; D066298:In Vitro Techniques; D008274:Magnesium; D009124:Muscle Proteins; D011817:Rabbits; D014357:Trypsin; D014783:Viscosity
chemical_list: D002614:Chelating Agents; D009124:Muscle Proteins; D014357:Trypsin; D000251:Adenosine Triphosphatases; D008274:Magnesium; D002122:Calcium Chloride