ATPgammaNH2 stabilizes the closed conformation of myosin subfragment 1 without cleavage of the beta-gamma phosphate bond, serving as a useful analog for studying myosin kinetics.
No immediate clinical implications; leaves open utility as a myosin kinetics tool in cardiovascular models.
On binding to myosin subfragment 1 (S1), the gamma-amido derivative of ATP (ATPgammaNH2), an isomer of adenosine 5'-[beta,gamma-imido]-triphosphate (AMPPNP), induces a larger increase in the intrinsic (tryptophan) fluorescence than is seen with ATP. A binding constant of 1.7x10(7) M(-1) was measured for ATPgammaNH2, compared to 2.1-2.4x10(7) M(-1) for AMPPNP. ATPgammaNH2 was hydrolyzed only very slowly by S1. ATPgammaNH2 appears to stabilize the 'closed' conformation of S1, and does so without cleavage of the beta-gamma phosphate bond. The dissociation of actin-S1 by ATPgammaNH2 and that of S1.ATPgammaNH2 by actin are both strikingly slow.
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Wray et al. (2002) studied this question.
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