Fluorescence studies of 1,N6-ethenoadenosine triphosphate bound to G-actin: the nucleotide base is inaccessible to water |
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Authors: | Harvey S C Cheung H C |
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Institution: | Biophysics Section, Department of Biomathematics, University of Alabama in Birmingham 35294, Birmingham, Alabama, USA. |
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Abstract: | When 1,N6-ethenoadenosine triphosphate (epsilon-ATP) is free in solution, its fluorescence is collisionally quenched by iodide ion, by methionine, by tryptophan, and by cysteine. None of these quenches the fluorescence of epsilon-ATP bound to G-actin. Thus, the ethenoadenine base is bound in a region of the protein which is inaccessible to collisions with these reagents. Since we have previously shown that the fluorescence of epsilon-ATP is quenched by water, the long lifetime of epsilon-ATP bound to G-actin (36 nsec, vs 27 nsec for epsilon-ATP in water) indicates that the bound nucleotide base is inaccessible to collisional quenching by water molecules. |
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