The mechanisms of ATP hydrolysis accompanying the polymerization of Mg-actin and Ca-actin.
The hydrolysis of ATP that accompanies actin polymerization occurs on the F-actin subsequent to the elongation step. For Mg-actin, the rate of ATP hydrolysis is similar to the rate of elongation at low concentrations of G-actin but increases more slowly as the G-actin concentration is increased. This behavior can be quantitatively modeled by assuming that ATP hydrolysis occurs predominantly, but not exclusively, on a single subunit of Mg-F-actin at the interface between an ATP-subunit cap and an ADP-subunit core. The rates of elongation of Ca-actin and Mg-actin are similar but the rate of ATP hydrolysis on Ca-F-actin is appreciably slower than the rate of elongation at all concentrations of Ca-G-actin. The data for Ca-actin can be modeled by assuming that ATP hydrolysis occurs essentially randomly on Ca-F-actin within a large ATP cap which can be as long as 2,000 subunits in a 10,000-subunit long filament.
D009327:4-Chloro-7-nitrobenzofurazan; D000199:Actins / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005456:Fluorescent Dyes; D006868:Hydrolysis; D007460:Iodoacetamide / Q000031:analogs & derivatives*; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism*; D011108:Polymers / Q000378:metabolism*; D011721:Pyrenes; D011817:Rabbits; D013050:Spectrometry, Fluorescence
D000199:Actins; D005456:Fluorescent Dyes; D011108:Polymers; D011721:Pyrenes; C029358:N-(1-pyrenyl)iodoacetamide; D000255:Adenosine Triphosphate; D009327:4-Chloro-7-nitrobenzofurazan; D008274:Magnesium; D002118:Calcium; D007460:Iodoacetamide