Low concentrations of guanidinium chloride expose apolar surfaces and cause differential perturbation in catalytic intermediates of rhodanese.

摘要: Abstract The conformations of sulfur-free and sulfur-containing rhodanese were followed with without the detergent lauryl maltoside after guanidinium chloride (GdmCl) addition to 5 M study apparent irreversibility denaturation. Without maltoside, denatured in a transition giving, at approximately 2.3 GdmCl, 50% total denaturation induced change observed by activity, CD, or intrinsic fluorescence. Sulfur-free gave more complex behavior fluorescence CD. CD showed loss secondary structure broad, complex, apparently biphasic extending from 0.5 3 GdmCl. interpretation was complicated time-dependent aggregation due noncovalent interactions. Results apolar probe 2-anilinonaphthalene-8-sulfonic acid, implicated exposure aggregation. Sulfhydryl reactivity indicated that low GdmCl concentrations intermediates affecting active site conformation. Lauryl prevented no effect on activity any conformational parameter native enzyme. Transitions still consistent several phases. Even an increase detected protein adsorption octyl-Sepharose well below major unfolding transitions. These results are interpreted model which interdomain interactions disrupted, thereby increasing accessibility, before intradomain