FIGURE 2.

Identification of Hsp90 as a (−)-maackiain-binding protein. A, fluorescence quenching assay. The fractions obtained from the anion exchange column chromatography were incubated with 1 μl of 100 mm (−)-maackiain, and intrinsic tryptophan-derived fluorescence was measured (inset). For the blank, DMSO without (−)-maackiain was added to the fractions. B, silver-stained SDS-polyacrylamide gel of fraction 16 that showed high quenching activity. Hsp90 was identified from the MS/MS analysis. C, quenching of intrinsic tryptophan fluorescence of recombinant Hsp90 by (−)-maackiain. A.U., arbitrary units.