Interaction of Bovine Serum Albumin and Metallothionein

Far UV circular dichroism (CD) and fluorescence spectroscopy were used to investigate the interaction between bovine serum albumin (BSA) and metallothionein (MT). Both spectroscopic probes gave proofs on the interaction of the two proteins. At pH 4.0, 7.0 and 9.0, BSA showed a negative increase in ellipticity at the far-UV range in the presence of MT indicating an increase in a-helical content and a decrease in β-sheet structure. In the presence of MT at pH 4.0 and 9.0, a decrease in fluorescence intensity was observed. Tryptophan fluorescence quenching experiments were also performed using acrylamide and KI as quenchers. Under acidic conditions, a four-fold increase in Stern-Volmer constant (KSV) was observed for BSA + MT. At neutral and basic conditions, a decrease in KSV values were observed which indicates conformational changes in BSA upon binding MT. These changes are close to the region where the tryptophan residues are located in the protein.