title: Direct evidence for ADP-Pi-F-actin as the major intermediate in ATP-actin polymerization. Rate of dissociation of Pi from actin filaments.
abstract: The sequence of reactions involved in the polymerization of ATP-actin and accompanying hydrolysis of ATP has been investigated by using a new glass-fiber filter assay. The assay allows the rapid separation of filaments from monomeric actin, and therefore the straightforward identification of the nucleotide bound to F-actin in the time course of polymerization, using double-labeled [gamma-32P,3H]ATP. The data bring a direct confirmation of the existence of the previously proposed ATP-F-actin intermediate in the time course of polymerization. Moreover, comparison of the hydrolyzed ATP (i.e., acid-labile [32P]Pi) and of 32P bound to F-actin provides direct evidence for the second intermediate ADP-Pi-F-actin in the polymerization process. This latter species is the major transient in the polymerization of ATP-actin, its lifetime being of the order of minutes.
mesh_terms: D000199:Actins / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D007700:Kinetics; D046911:Macromolecular Substances; D009132:Muscles / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism*; D010761:Phosphorus Radioisotopes; D011817:Rabbits
chemical_list: D000199:Actins; D046911:Macromolecular Substances; D010710:Phosphates; D010761:Phosphorus Radioisotopes; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate