title: The bound nucleotide of actin.
abstract: The extent of actin polymerization has been studied for samples in which the bound nucleotide of the actin was ATP, ADP, or an analog of ATP that was not split (AMPPNP). The equilibrium constants for the addition of a monomer to a polymer end were determined from the concentration of monomer coexisting with the polymer. An analysis of these results concludes that the bound ATP on G-actin provides little energy to promote the polymerization of the actin. AMPPNP was incorporated into F-actin and the interaction of F-actin - AMPPNP with  myosin was studied. F-actin - AMPPNP activated the ATPase of myosin to the same extent as did F-actin - ADP. However, the rate of superprecipitation was slower in the case of F-actin - AMPPNP than in the control.
mesh_terms: D000199:Actins / Q000378:metabolism*; D000205:Actomyosin / Q000378:metabolism; D000244:Adenosine Diphosphate / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism*; D000266:Adenylyl Imidodiphosphate / Q000378:metabolism*; D001665:Binding Sites; D011232:Chemical Precipitation; D009218:Myosins / Q000378:metabolism; D011108:Polymers / Q000378:metabolism
chemical_list: D000199:Actins; D011108:Polymers; D000266:Adenylyl Imidodiphosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D000205:Actomyosin; D000251:Adenosine Triphosphatases; D009218:Myosins