Refolding of denatured trichosanthin in the presence of GroEL.

The stability of trichosanthin (TCS), a 27-kDa ribosome-inactivating protein, was investigated in the presence of guanidinium chloride (GdnHCl). The process of unfolding was monitored by CD and fluorescence spectroscopy. Both methods show the presence of partially folded intermediates. Unfolding of TCS is attained in 6M GdnHCl, but the inactive species recover a good deal of its DNase activity upon dilution with buffer containing GroEL and ATP. The mechanism of recognition of unfolded TCS by GroEL was studied by fluorescence spectroscopy.