期刊
JOURNAL OF MOLECULAR BIOLOGY
卷 326, 期 4, 页码 1227-1237出版社
ACADEMIC PRESS LTD ELSEVIER SCIENCE LTD
DOI: 10.1016/S0022-2836(02)01443-2
关键词
protein stability; molecular crowding; molten globule; excluded volume; dextran
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. (C) 2003 Elsevier Science Ltd. All rights reserved.
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