期刊
ACTA BIOCHIMICA ET BIOPHYSICA SINICA
卷 44, 期 8, 页码 703-711出版社
OXFORD UNIV PRESS
DOI: 10.1093/abbs/gms052
关键词
human -lactalbumin; macromolecular crowding; protein stability; fluorescence spectroscopy; circular dichroism; trypsin digestion
资金
- National Key Basic Research Foundation of China [2012CB911003]
- National Natural Science Foundation of China [30970599, 31170744]
- Fundamental Research Funds for the Central Universities of China [1104006]
The folding of protein, an important process for protein to fulfill normal functions, takes place in crowded physiological environments. -Lactalbumin, as a model system for protein-folding studies, has been used extensively because it can form stable molten globule states under a range of conditions. Here we report that the crowding agents Ficoll 70, dextran 70, and polyethylene glycol (PEG) 2000 have different effects on the structural stability of human -lactalbumin (HLA) represented by the transition to a molten globule state: dextran 70 dramatically enhances the thermal stability of Ca-2-depleted HLA (apo-HLA) and Ficoll 70 enhances the thermal stability of apo-HLA to some extent, while PEG 2000 significantly decreases the thermal stability of apo-HLA. Ficoll 70 and dextran 70 have no obvious effects on trypsin degradation of apo-HLA but PEG 2000 accelerates apo-HLA degradation by trypsin and destabilizes the native conformation of apo-HLA. Furthermore, no interaction is observed between apo-HLA and Ficoll 70 or dextran 70, but a weak, non-specific interaction between the apo form of the protein and PEG 2000 is detected, and such a weak, non-specific interaction could overcome the excluded-volume effect of PEG 2000. Our data are consistent with the results of protein stability studies in cells and suggest that stabilizing excluded-volume effects of crowding agents can be ameliorated by non-specific interactions between proteins and crowders.
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