Del Rizzo Paul A, Bi Yumin, Dunn Stanley D
Department of Biochemistry, University of Western Ontario, London, Ontario, Canada, N6A 5C1.
J Mol Biol. 2006 Dec 8;364(4):735-46. doi: 10.1016/j.jmb.2006.09.028. Epub 2006 Sep 14.
The dimerization domain of Escherichia coli ATP synthase b subunit forms an atypical parallel two-stranded coiled coil. Sequence analysis reveals an 11-residue abcdefghijk repeat characteristic of right-handed coiled coils, but no other naturally occurring parallel dimeric structure of this class has been identified. The arrangement of the helices was studied by their propensity to form interhelix disulfide linkages and analysis of the stability and shape of disulfide-linked dimers. Disulfides formed preferentially between cysteine residues in an a position of one helix and either of the adjacent h positions of the partner. Such heterodimers were far more stable to thermal denaturation than homodimers and, on the basis of gel-filtration chromatography studies, were similar in shape to both non-covalent dimers and dimers linked through flexible Gly(1-3)Cys C-terminal extensions. The results indicate a right-handed coiled-coil structure with intrinsic asymmetry, the two helices being offset rather than in register. A function for the right-handed coiled coil in rotational catalysis is proposed.
大肠杆菌ATP合酶b亚基的二聚化结构域形成一种非典型的平行双链卷曲螺旋。序列分析揭示了一种11个残基的abcdefghijk重复序列，这是右手卷曲螺旋的特征，但尚未鉴定出该类别的其他天然存在的平行二聚体结构。通过它们形成螺旋间二硫键的倾向以及对二硫键连接的二聚体的稳定性和形状分析来研究螺旋的排列。二硫键优先在一个螺旋的a位置的半胱氨酸残基与伙伴的相邻h位置之一之间形成。这种异源二聚体对热变性的稳定性远高于同源二聚体，并且基于凝胶过滤色谱研究，其形状与非共价二聚体以及通过柔性Gly(1-3)Cys C末端延伸连接的二聚体相似。结果表明存在一种具有内在不对称性的右手卷曲螺旋结构，两个螺旋相互错开而非对齐。提出了右手卷曲螺旋在旋转催化中的作用。
