Chromium(III) mediated conformational changes associated with alterations in the enzymatic activity of BSA: Influence of the coordinated ligand

Abstract

Interaction of three chromium(III) complexes, [Cr(salen)(H₂O)₂]ClO₄<b>(1)</b>, Na[Cr(EDTA)(H₂O)] <b>(2)</b> and [Cr(en)₃]Cl₃ <b>(3)</b> with bovine serum albumin (BSA) has been investigated in order to understand the role of coordinated ligand in mediating the interaction between the protein and chromium(III) ion. Binding of <b>(1)</b> and <b>(2)</b> to BSA has been found to result in increase in the esterase activity of BSA from 2.41 to 2.72 and 2.62 U/L respectively. On the other hand, binding of <b>(3)</b> results in decrease of the activity from 2.41 to 1.91 U/L. These changes in the esterase activity are also reflected in the conformation of BSA in the presence of <b>(1)</b>, <b>(2)</b> and <b>(3)</b>. CD spectrum of BSA clearly indicates that binding of <b>(1)</b> and <b>(2)</b> leads to increase in the helicity of BSA, whereas binding of <b>(3)</b> leads to decrease in the helicity of the protein. Such a change in the helicity of BSA leads to change in the orientation of active amino acids (Tyr ₄₁₁ and Arg ₄₁₀) in the protein, thus affecting the esterase activity of protein. The nature of the coordinated ligand has also been found to influence the stability of BSA against trypsin digestion.