Thermally induced transition curves of hen egg-white lysozyme were measured in the presence of several concentrations of dextran at pH 2.0 by near-UV and far-UV CD. The transition curves were fitted to a two-state model by a non-linear, least-squares method to obtain the transition temperature (T(m)), enthalpy change (deltaH(u)(T(m))), and free energy change (deltaG(u)(T)) of the unfolding transition. An increase in T(m) and almost constant deltaH(u)(T(m)) values were observed in the presence of added dextran at concentrations exceeding ca 100 g l(-1). In addition, dextran-induced conformational changes of fully unfolded protein were investigated by CD spectroscopy. Addition of high concentrations of dextran to solutions of acid-unfolded cytochrome c at pH 2.0 results in a shift of the CD spectrum from that characteristic of the fully unfolded polypeptide to that characteristic of the more compact, salt-induced molten globule state, a result suggesting that the molten globule-like state is stabilized relative to the fully unfolded form in crowded environments. Both observations are in qualitative accord with predictions of a previously proposed model for the effect of intermolecular excluded volume (macromolecular crowding) on protein stability and conformation. Study holds ProTherm entries: 16230, 16231, 16232, 16233, 16234, 16235, 16236, 16237, 16238, 16239, 16240, 16241, 16242, 16243, 16244, 16245 Extra Details: (i) at 289 nm protein stability; molecular crowding; molten globule; excluded volume; dextran
ID: PCSoUTst
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:47 p.m.
Version: 1
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