Binding of 1,N6-ethanoadenosine triphosphate to actin |
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Authors: | K E Thames H C Cheung S C Harvey |
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Institution: | Department of Biomathematics, University of Alabama in Birmingham University Station, Birmingham, Alabama 35294 USA |
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Abstract: | G-actin is known to bind one molecule of ATP. Its polymerization to F-actin is accompanied by the splitting off of the terminal phosphate of the bound nucleotide. We have found that the fluorescent 1,N6-ethanoadenosine triphosphate (?ATP) can substitute for ATP in G-actin and that G-actin containing bound ?ATP possesses essentially full polymerizability. The binding of this ATP analog has been studied by following the inactivation of the ?ATP·G-actin complex. The binding constant (4?5.7 × 106 M?1) obtained in the absence of EDTA is about 50% of that for ATP, while the binding constant obtained in the presence of EDTA (0.9?3.0 × 105 M?1) is comparable to those for ATP and ADP. These findings suggest that ?ATP can be used as a structural probe for actin. The fluorescence lifetime of ?ATP bound to G·actin is 36 nsec. The rotational relaxation time of ?ATP·G-actin is near 60 nsec. at 20°C. |
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