Characterization of acid-induced molten globule like state of ficin.

Effect of pH on the conformational behaviour of ficin (EC 3.4.22.3), a cysteine protease from the latex of Ficus carica was monitored by circular dichroism, fluorescence spectroscopy, ANS binding and hydrodynamic studies. The results obtained from near- and far-UV CD, intrinsic fluorescence and ANS binding studies demonstrate that ficin exhibits the characteristic properties of molten globule at acidic conditions between pH 1.4 and 2.0. Ficin at pH 1.4 retained about approximately 74% secondary structure with a substantial loss of tertiary structure. The acid-induced state was found to have a compact shape as measured by Stokes radius on size exclusion chromatography.