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 ∼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.