Visualization of F-actin filaments by a fluorescently labeled nucleotide analogue.

ABSTRACT

The tightly-bound nucleotide of F-actin was replaced with 1,N6-etheno-adenosine ATP (ADP). An epi-fluorescence optical microscope was modified to visualize efficiently the fluorescent analogue with an excitation-maximum wavelength of 310 nm. This microscope permitted us to visualize single F-actin filaments in solution using the fluorescence of the strongly bound 1,N6-ethenoadenosine nucleotide. Exchange of the tightly-bound nucleotide of F-actin with a free nucleotide in solution at a high temperature was quantitatively estimated by this method, and the results showed good agreement with results from phosphate release measurements.