Parry D A, Minasian E, Leach S J
Department of Physics and Biophysics, Massey University, Palmerston North, New Zealand.
J Mol Recognit. 1991 Mar-Jun;4(2-3):63-75. doi: 10.1002/jmr.300040205.
The amino acid sequences of human and murine haemopoietins have been analysed using algorithms predictive for secondary structure. The results for 19 of these proteins (human and murine interleukins 2, 3, 4, 5, 6, 7 and granulocyte, macrophage and granulocyte macrophage-colony stimulating factors as well as human erythropoietin) suggest that they each contain a 4-alpha-helical bundle, ca 25 A long, as a common conformational feature. The most important predictive indicator was considered to be the occurrence of quasi-repeating sequences of seven amino acids of the form (a-b-c-d-e-f-g), with apolar side chains (usually leucine) lying alternately three and four residues apart in the a and d positions. As with other proteins of known secondary structure this periodicity favours the formation of alpha-helical elements, each with an apolar external strip, which interdigitate closely with one another when tested appropriately. Molecular models based on these putative 4-alpha-helical bundles are presented--with special reference to human granulocyte macrophage-colony stimulating factor. The extent to which such models are consistent with experiments designed to delineate receptor binding sites is discussed.
已使用预测二级结构的算法分析了人和小鼠造血蛋白的氨基酸序列。其中19种蛋白质（人及小鼠白细胞介素2、3、4、5、6、7以及粒细胞、巨噬细胞和粒细胞巨噬细胞集落刺激因子，还有人促红细胞生成素）的分析结果表明，它们均含有一个约25埃长的4-α-螺旋束，这是一个共同的构象特征。最重要的预测指标被认为是形式为（a-b-c-d-e-f-g）的七个氨基酸的准重复序列的出现，其中非极性侧链（通常为亮氨酸）在a和d位置交替相隔三个和四个残基。与其他已知二级结构的蛋白质一样，这种周期性有利于形成α-螺旋元件，每个元件都有一个非极性外部条带，在适当测试时它们会彼此紧密交错。给出了基于这些假定的4-α-螺旋束的分子模型——特别提及了人粒细胞巨噬细胞集落刺激因子。讨论了此类模型与旨在描绘受体结合位点的实验的一致程度。
