Comparison of the denaturant-induced unfolding of the bovine and human α-lactalbumin molten globules

被引:47
作者
Wijesinha-Bettoni, R [1 ]
Dobson, CM [1 ]
Redfield, C [1 ]
机构
[1] Univ Oxford, Oxford Ctr Mol Sci, Cent Chem Lab, Oxford OX1 3QH, England
基金
英国惠康基金; 英国工程与自然科学研究理事会; 英国医学研究理事会; 英国生物技术与生命科学研究理事会;
关键词
alpha-lactalbumin; molten globule state; protein folding; urea unfolding; NMR;
D O I
10.1006/jmbi.2001.4927
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Residue-specific information on the urea-induced unfolding of the molten globule state of bovine alpha -lactalbumin (BLA) has been obtained using NMR spectroscopy. In agreement with previous studies on human alpha -lactalbumin (HLA) the unfolding process for BLA has been found to be non-cooperative. Both the alpha and beta -domains of the protein are substantially collapsed in the absence of denaturant but in both proteins the majority of the structure in the beta -domain unfolds prior to that in the alpha -domain. However, in BLA the protein unfolds completely in 10 M urea at 50 degreesC, whilst in HLA a stable core region persists even under these extreme conditions. Previous studies on HLA have identified eight residues that are crucial for the stability of the molten globule. Of these residues, only three are conserved in the sequence of BLA. By taking into consideration the differences in inter-residue contacts between the four alpha -helices arising from these substitutions, and the relative hydrophobicity of the helices in the two proteins, we show that it is possible to rationalise the observed differences in the behaviour of the molten globule states of the two proteins. Taken together, these results suggest that there may be a number of ways of stabilising a given protein fold, and the specific manner that this is achieved for a particular protein is determined by details of its sequence. (C) 2001 Academic Press.
引用
收藏
页码:261 / 273
页数:13
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