The influence of intersubunit cross-linking on the conformational changes of creatine kinase during denaturation by guanidine hydrochloride.

Intersubunit cross-linked creatine kinase (CK) has been prepared with the cross-linking reagent dithiobis(succinimidyl propionate) (DTSP). Unfolding of cross-linked CK during denaturation by guanidine hydrochloride (GuHCl), as monitored by intrinsic fluorescence, circular dichroism and fluorescence of the hydrophobic probe, 1-aniline-naphthalene-8-sulfonate (ANS), occurs in two stages with increasing GuHCl concentration. The process is similar to that of the unmodified enzyme, but in the second stage, conformational changes of the cross-linked enzyme need higher concentration of GuHCl, suggesting that there is a stable intermediate during its unfolding transition and the intermediate is stabilized by intersubunit cross-linkage.