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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| http://dx.doi.org/10.1016/s0014-5793(02)02654-6 | DOI Listing |
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