Interaction of horse plasma gelsolin with the hydrophobic fluorescent probe 2-(N-methylanilino)naphthalene-6-sulfonic acid.

Addition of horse plasma gelsolin to solutions of the fluorescent probe 2-(N-methylanilino)naphthalene-6-sulfonic acid (MANS) results in both a considerable enhancement and blue-shift of the MANS emission, indicative of hydrophobic interaction between MANS and gelsolin. Titrations suggest each gelsolin to bind two to three molecules of MANS, with a dissociation constant for each site of 0.24 microM. The peptide bond circular dichroism of gelsolin is unaffected by interaction with MANS, and viscosity data indicate that MANS does not inhibit the effects of gelsolin on actin polymerization. Fluorescence polarization data confirm gelsolin to be a globular protein and thermal denaturation studies suggest a cooperative melting transition for plasma gelsolin near 46 degrees C.