Whitlow M, Teeter M M
Department of Chemistry Boston University, MA 02215.
J Biomol Struct Dyn. 1985 Feb;2(4):831-48. doi: 10.1080/07391102.1985.10506327.
Homologous proteins may fold into similar three-dimensional structures. Spectroscopic evidence suggests this is true for the cereal grain thionins, the mistletoe toxins, and for crambin, three classes of plant proteins. We have combined primary sequence homology and energy minimization to predict the structures alpha 1-purothionin (from Durum wheat) and viscotoxin A3 (from Viscum album, European mistletoe) from the high resolution (0.945 A) crystal structure of crambin (from Crambe abyssinica). Our predictions will be verifiable because we have diffraction-quality crystals of alpha 1-purothionin whose structure we are have predicted. The potential energy minimizations for each protein were performed both with and without harmonic constraints to its initial backbone to explore the existence of local minima for the predicted proteins. Crambin was run as a control to examine the effects of the potential energy minimization on a protein with a well-known structure. Only alpha 1-purothionin which has one fewer residue in a turn region shows a significant difference for the two minimization paths. The results of these predictions suggest that alpha 1-purothionin and viscotoxin are amphipathic proteins, and this character may relate to the mechanism of action for these proteins. Both are mildly membrane-active and their amphipatic character is well suited for interaction with a lipid bilayer.
同源蛋白质可能折叠成相似的三维结构。光谱学证据表明，对于谷物硫堇、槲寄生毒素和胰凝乳蛋白酶原这三类植物蛋白来说确实如此。我们结合一级序列同源性和能量最小化方法，根据胰凝乳蛋白酶原（来自阿比西尼亚芥）的高分辨率（0.945埃）晶体结构，预测了α1-硫堇蛋白（来自硬粒小麦）和槲寄生毒素A3（来自欧洲槲寄生）的结构。我们的预测将是可验证的，因为我们拥有已预测其结构的α1-硫堇蛋白的衍射质量晶体。对每种蛋白质的势能最小化分别在对其初始主链有和没有谐波约束的情况下进行，以探索预测蛋白质局部最小值的存在。将胰凝乳蛋白酶原作为对照运行，以研究势能最小化对具有已知结构的蛋白质的影响。只有在转角区域少一个残基的α1-硫堇蛋白在两条最小化路径上显示出显著差异。这些预测结果表明，α1-硫堇蛋白和槲寄生毒素是两亲性蛋白质，这种特性可能与这些蛋白质的作用机制有关。两者都具有轻度的膜活性，它们的两亲性特性非常适合与脂质双层相互作用。
