Bulaj G, Goldenberg D P
Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, Utah 84112-0840, USA.
Nat Struct Biol. 2001 Apr;8(4):326-30. doi: 10.1038/86200.
Amino acid replacements were used to probe the roles of 14 sites in two well-characterized intermediates in the folding pathway of bovine pancreatic trypsin inhibitor (BPTI). One of these intermediates contains one of the three disulfides found in the native protein (30--51). NMR studies have shown that approximately two-thirds of this polypeptide has a native-like conformation. The other intermediate contains two native disulfides (30--51 and 5--55) and has a fully folded conformation. The phi-values for a majority of residues were <1, indicating that the native protein was significantly more destabilized than either intermediate even when the altered residue was located in a well-ordered region of the intermediate. These observations suggest that folding intermediates and transition states may generally be more structured than indicated by phi-values alone.
氨基酸替换被用于探究牛胰蛋白酶抑制剂（BPTI）折叠途径中两个特征明确的中间体中14个位点的作用。其中一个中间体包含天然蛋白质中发现的三个二硫键之一（30 - 51）。核磁共振研究表明，该多肽约三分之二具有类似天然的构象。另一个中间体包含两个天然二硫键（30 - 51和5 - 55），具有完全折叠的构象。大多数残基的φ值<1，这表明即使改变的残基位于中间体的有序区域，天然蛋白质也比任何一个中间体明显更不稳定。这些观察结果表明，折叠中间体和过渡态通常可能比仅由φ值所表明的结构更有序。
