STEADY-STATE FLUORESCENCE STUDY OF THE INTERACTION OF CRESYL VIOLET PERCHLORATE WITH TUBULIN

The interaction of cationic and anionic dyes with tubulin has been inv estigated using fluorescence spectroscopic techniques. Cresyl violet p erchlorate (CV) and 3,3'-diethyloxadicarbocyanine iodide (DiOC2(5)) wh ich are cationic dyes and resorufin, an anionic dye, have been used in this investigation. It has been found that CV affects the polymerizat ion of tubulin while resorufin and DiOC2(5) do not affect the polymeri zation. The results suggest that CV interacts with tubulin in a manner different from the more frequently used fluorescent probes, ANS and b is-ANS. CV has more than one binding site on the protein and probably binds in the ANS binding region as well as the colchicine binding regi on on the protein. Our results establish that the structure rather tha n the charge on the molecule is important for affecting the polymeriza tion of tubulin.