CALCIUM-BINDING AND SALT-INDUCED STRUCTURAL-CHANGES OF NATIVE AND PREHEATED BETA-LACTOGLOBULIN

Calcium binding to beta-lactoglobulin in the native and preheated forms was studied using an ion-selective electrode, and the structural changes induced were studied by fluorescence spectroscopy. Ca binding to beta-lactoglobulin showed a small increase with heat treatment and a larger increase with pH. The intrinsic fluorescence of beta-lactoglobulin and aniline naphthalenesulfonate fluorescence showed significant increases with heat treatment and with the addition of CaCl2 (1-15 mM). The reactive sulfhydryl group content also increased with the addition of CaCl2 to native and preheated beta-lactoglobulin. Addition of Na to beta-lactoglobulin showed smaller changes than did addition of Ca. Intrinsic fluorescence and ANS fluorescence increased slightly, and the reactive sulfhydryl content decreased with the addition of Na to preheated beta-lactoglobulin. Our results show that Ca binding interaction of beta-lactoglobulin induces small structural changes in beta-lactoglobulin which lead to increased hydrophobicity. The results also indicate that hydrophobic interaction plays a major role during salt-induced gelation.