Effect of galactose on acid induced molten globule state of Soybean Agglutinin: Biophysical approach

• The molten globule state of SBA exist at pH 2.2.
• The maximum exposure of hydrophobic patches was found to be at pH 2.2.
• Hydrodynamic radii of SBA were significantly increased at pH 2.2 as compared to native state at pH 7.
• Galactose does not have much influence on the molten globule state of SBA.

In the present study the formation of molten globule-like unfolding intermediate Soybean Agglutinin (SBA) in acidic pH range has been established with the help of acrylamide quenching, intrinsic fluorescence, ANS fluorescence measurement, far UV CD and dynamic light scattering measurement. A marked increase in ANS fluorescence was observed at pH 2.2. Ksv of acrylamide quenching was found to be higher at pH 2.2 than that of native SBA at pH 7. Far UV CD spectra of pH induced state suggest that SBA shows significant retention of secondary structure closure to native. Hydrodynamic radius of SBA at pH 2.2 was found be more as compared to native state and also in other pH induced states. Further we checked the effect of galactose on the molten globule state of SBA. This study suggests that SBA exist as molten globule at pH 2.2 and this study will help in acid induced molten globule state of other proteins.