Key result
AMPPNP strongly suppressed the ATPase inactivation of squid myosin subfragment-1, achieving approximately 50-fold stabilization, though this effect was lost at high KCl concentrations.
AMPPNP strongly stabilizes squid myosin subfragment-1 against thermal denaturation, but this effect is not additive with F-actin stabilization and is lost at high KCl concentrations.
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No direct clinical relevance for cardiovascular practice; leaves open mechanistic studies of myosin stabilization in non-mammalian models.
Adenosine triphosphatase (ATPase) inactivation of squid myosin subfragment-1 (S-1) was strongly suppressed upon addition of adenylimidophosphate (AMPPNP), an analogous compound of adenosine triphosphate (ATP); whereas suppression by adenosine diphosphate (ADP) and pyrophosphate (PPi) was not as effective. Adenylimidophosphate did not stabilize myofibrils in which myosin is stabilized by F-actin. Thus, the stabilization effect by F-actin and AMPPNP is not additive. Pyrophosphate markedly accelerated the inactivation of myofibrils through the loss of protection by F-actin. The suppressive effect of F-actin on myosin ATPase inactivation was much greater than that by AMPPNP. The stabilization effects of AMPPNP and F-actin on S-1 were almost completely lost when the medium contained approximately 1 M KCl.
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Yoshioka et al. (2002) studied this question. AMPPNP (adenylimidophosphate) vs. No compound, ADP, or PPi was evaluated on Ca2+-ATPase inactivation rate constant (KD). AMPPNP strongly suppressed the ATPase inactivation of squid myosin subfragment-1, achieving approximately 50-fold stabilization, though this effect was lost at high KCl concentrations.
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