The presence of nucleotides and nucleotide analogues affects the equilibrium between the strongly bound and weakly bound states of actin and myosin subfragment 1.
The binding of actin to myosin subfragment 1 (S1) has been shown to occur as a two-step reaction Coates, Criddle & Geeves (1985) Biochem. J. 232, 351-356. In the first step actin is weakly bound and the second step involves the complex isomerizing to a more tightly bound state. This isomerization can be followed specifically by monitoring the fluorescence of actin that has been covalently labelled with N-(pyren-1-yl)-iodoacetamide at Cys-374 Geeves, Jeffries & Millar (1986) Biochemistry 25, 8454-8458. We report here that the presence of nucleotides and nucleotide analogues affects the equilibrium between the strongly bound and weakly bound states (referred to as K2). In the presence of ATP, gamma-thioATP or ADP and vanadate a value of approx. less than 10(-2) was estimated for K2. In the presence of PPi or ADP a value of approx. 2.3 or 10 respectively was obtained. An increase in KCl concentration or the presence of 40% ethylene glycol was found to decrease K2 in the presence of ADP. The data presented here are consistent with the two-step binding model proposed by Geeves, Goody & Gutfreund (1984) J. Muscle Res. Cell Motil. 5, 351-361, where it was suggested that the transition between weakly bound and strongly bound states is closely associated with the force-generating event in whole muscle.
Geeves et al. (Tue,) reported a other. Nucleotides and nucleotide analogues was evaluated on Equilibrium between strongly bound and weakly bound states (K2). The presence of nucleotides and nucleotide analogues affects the equilibrium between the strongly bound and weakly bound states of actin and myosin subfragment 1.
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