Abstract

In continuation of earlier work [Hu, C. Q., & Sturtevant, J.M. (1987) Biochemistry 26, 178-182], differential scanning calorimetry has been employed in a study of the effects on the thermal denaturation of yeast phosphoglycerate kinase of two inhibitors of the enzyme, sulfate ion and the dye Cibracron blue F3GA. Sulfate ion, as is usual with ligands that dissociate during unfolding of the host protein, raises t1/2, the temperature of half-completion of the denaturation, has only a modest effect, stemming from the enthalpy of dissociation of the ligand, on the enthalpy of denaturation, and has little or no effect on the heat capacity change resulting from denaturation. In sharp contrast, Cibacron blue F3GA lowers t1/2 and drastically decreases both the enthalpy and heat capacity changes due to denaturation. The DSC results with sulfate ion are consistent with previous kinetic data [Scopes, R. K. (1978) Eur. J. Biochem. 91, 119-129; Khamis, M. H., & Larsson-Raznikiewicz, M. (1981) Biochim. Biophys. Acta 657, 190-194], which indicate two binding sites for sulfate ion at one of which the ligand acts as a competitive inhibitor. The results with Cibacron blue F3GA indicate that the dye induces a major destabilizing structural change in the enzyme in addition to rendering it enzymically inactive. Study holds ProTherm entries: 3836, 10723, 10724, 10725, 10726, 10727, 10728, 10729, 10730, 10731, 10732, 10733, 10734, 10735, 10736, 10737, 10738, 10739, 10740, 10741, 10742, 10743, 10744, 10745, 10746, 10747, 10748, 10749, 10750, 10751, 10752, 10753, 10754, 10755, 10756, 10757, 10758, 10759, 10760, 10761, 10762, 10763, 10764, 10765, 10766, 10767, 10768, 10769, 10770, 10771, 10772, 10773, 10774, 10775, 10776, 10777, 10778, 10779, 10780, 10781, 10782, 10783, 10784, 10785, 10786, 10787, 10788 Extra Details: enthalpy of denaturation; heat capacity changes; structural change;,enzymically inactive

Submission Details

ID: 3hkdVH5X

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:22 p.m.

Version: 1

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