A fluorometric study of modification of bovine serum albumin with structural analogues of taurine chloramine

Abstract

We studied the effects of taurine chloramine and its structural analogues, antiplatelet agents, on the tertiary structure of bovine serum albumin by recording changes in its fluorescence spectrum. BSA was chosen as a model of the extracellular part of the purine P2Y12 receptor in platelets. For the detection of weak spectral shifts of the protein fluorescence, the index, which represents the ratio of the two light sums measured from approximately the middle of the spectrum towards the short- and longwave limits of its registration, was used. Administration of N-chlorotaurine and its analogues N-acetyl-N-chlorotaurine and N-isopropyl-N-chlorotaurine in albumin solution in equimolar concentrations cause weakening and red shift of the tryptophanyl fluorescence of the protein, indicating reorganization of the protein’s tertiary structure, thereby changing the properties of the microenvironment of tryptophan residues, primarily, Trp 134. All these changes are probably due to a covalent modification of the sulfhydryl group of Cys34 residue. It was hypothesized that chloramines of taurine have the ability to inhibit the activity of the ADP P2Y12 receptor in platelets due to the modification of its sulfhydryl group and that the inhibitory effect on the ADP-binding site has an allosteric character.