Mao B Y, Chou K C, Maggiora G M
Upjohn Research Laboratories, Kalamazoo, MI 49001.
Eur J Biochem. 1990 Mar 10;188(2):361-5. doi: 10.1111/j.1432-1033.1990.tb15412.x.
A recent study has shown that topological stereoisomers exist for the polypeptide chain in disulfide-containing proteins that are represented by non-planar graphs. This topological stereochemistry is demonstrated in the structure of variant 3 toxin in the venom of the North American scorpion Centruroides sculpturatus Ewing and the structure of toxin II from the North African scorpion Androctonus australis Hector. In this report, we found that a similar topological analysis can be applied to the hydrogen bonding in alpha-helices and beta-sheets within protein molecules, and we described the topological characteristics of chiral properties of protein secondary structure elements. Specifically, a closed right-handed alpha-helix of more than six residues long is shown formally to be non-planar and has the L topology. Antiparallel beta-sheets are planar. Two parallel beta-strands each of at least three residues in length, however, constitute a non-planar structural element and can have either L or D topology. The favored right-handed crossover for parallel beta-sheets has the L form, the same as the right-handed alpha-helix. This topological description of the hydrogen bonding in secondary structures may be extended to higher levels of protein structure and may provide a conceptual framework for studying complex protein architecture in general.
最近的一项研究表明，以非平面图表示的含二硫键蛋白质中的多肽链存在拓扑立体异构体。这种拓扑立体化学在北美雕刻纹毒蝎（Centruroides sculpturatus Ewing）毒液中的变体3毒素结构以及北非黄肥尾蝎（Androctonus australis Hector）的毒素II结构中得到了证明。在本报告中，我们发现类似的拓扑分析可应用于蛋白质分子内α螺旋和β折叠中的氢键，并且我们描述了蛋白质二级结构元件手性性质的拓扑特征。具体而言，长度超过六个残基的封闭右手α螺旋形式上是非平面的，具有L拓扑结构。反平行β折叠是平面的。然而，两条长度至少为三个残基的平行β链构成一个非平面结构元件，并且可以具有L或D拓扑结构。平行β折叠中最常见的右手交叉具有L形式，与右手α螺旋相同。二级结构中氢键的这种拓扑描述可能会扩展到更高层次的蛋白质结构，并且总体上可能为研究复杂的蛋白质结构提供一个概念框架。
