Kinetics of the cooperative association of actin to actin filament

摘要: The cooperative formation of actin filaments from monomers was followed by light scattering and electron microscopy. results are well described a simple model mechanism in which the growth destruction occurs stepwise addition or dissociation protomers. All steps except dimerisation step assumed to have identical rate constants. These were found be 5 X 10(3) M-1 - sec-1 3 10(-2) for association dissociation, respectively (at pH 7.5 presence 10(-3) M calcium chloride). equilibrium constant elongation as obtained critical concentration is 1.7 10(5) M-1. corresponding about 10 million times smaller (cooperativity parameter sigma = 2 10(-7)). This makes nucleation extremely difficult cooperativity very high. A best fit experimental data achieved when dimer much faster than third protomer (fast monomer- pre-equilibrium). size nucleus propagation becomes 3.