NaCl-induced conformational transition of the acid-unfolded state of staphylococcal nuclease

摘要

The acid-unfolded state(U_A)of staphylococcal nuclease(SNase)can fold into a state(Astate)in acidic solution of high NaCl concentration,that is,U_A→A.The transition curve of U_A→A inducedby the increasing of NaCl concentration was superimposed with that induced by the increasing of HClconcentration,indicating that the U_A → A transition is induced by the chloride anion being inclined to bind onsome parts of SNase molecules in A state.Circular dichroism(CD)spectra showed that A state hassubstantial secondary structure.Size exclusion chromatography measurement indicated that A state is compact involume.The A state can bind with 1-anilino-naphthalene-8-sulfonate(ANS),a fluorescent probe forhydrophobicity.These results indicated that A state of SNaseR is a molten globule-like state.Besides,ourresults showed that A state can be unfolded by guanidine hydrochloride(Gu · HCl),implying that thehydrophobic interaction between side chains in A state is responsible to its stabilization.