Kim D E, Yi Q, Gladwin S T, Goldberg J M, Baker D
Department of Biochemistry, University of Washington, Seattle, WA, 98195, USA.
J Mol Biol. 1998 Dec 4;284(3):807-15. doi: 10.1006/jmbi.1998.2200.
To investigate the role of helix formation in the folding of protein L, a 62 residue alpha/beta protein, we studied the consequences of both single and multiple mutations in the helix on the kinetics of folding. A triple mutant with 11 additional carbon atoms in core residues in the amino-terminal portion of the helix folded substantially faster than wild type, suggesting that hydrophobic association with residues elsewhere in the protein occurs at the rate-limiting step in folding. However, helix-destabilizing mutations had little effect on the rate of folding; in particular, a triple glycine substitution on the solvent-exposed side of the helix increased the unfolding rate 56-fold while reducing the folding rate less than threefold. Thus, in contrast to the predictions of models of folding involving the coalescence of well-formed secondary structure elements, the single helix in protein L appears to be largely disrupted at the rate-limiting step in folding and unfolding.
为了研究螺旋形成在62个残基的α/β蛋白L折叠过程中的作用，我们研究了螺旋中单个和多个突变对折叠动力学的影响。在螺旋氨基末端部分的核心残基中有11个额外碳原子的三重突变体折叠速度比野生型快得多，这表明与蛋白质其他部位残基的疏水缔合发生在折叠的限速步骤。然而，螺旋不稳定突变对折叠速率影响很小；特别是，螺旋溶剂暴露侧的三重甘氨酸取代使解折叠速率增加了56倍，而折叠速率降低不到三倍。因此，与涉及结构良好的二级结构元件合并的折叠模型预测相反，蛋白L中的单螺旋在折叠和解折叠的限速步骤似乎大部分被破坏。
