Helix packing in polytopic membrane proteins: Role of glycine in transmembrane helix association
Helix packing in polytopic membrane proteins: Role of glycine in transmembrane helix association
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DOI：
10.1016/s0006-3495(99)77009-8
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发表时间：
1999-09-01
影响因子：
3.4
通讯作者：
Smith, SO
中科院分区：
文献类型：
--
作者：
Javadpour, MM;Eilers, M;Smith, SO
研究了四种多面体膜蛋白（细胞色素 C 氧化酶、细菌视紫红质、球形红细菌的光合反应中心和浅青紫链霉菌的钾通道）螺旋界面中氨基酸的性质和分布，以解决甘氨酸在跨膜螺旋堆积中的作用。与甘氨酸是著名的螺旋破坏剂的可溶性蛋白质相反，跨膜螺旋中甘氨酸的主链二面角大部分落在拉马钱德兰图的标准α螺旋区域内。对螺旋堆积的分析表明，这些蛋白质的跨膜区域中的甘氨酸残基主要面向螺旋-螺旋界面，并且在螺旋交叉点处出现率很高。此外，折叠蛋白质结构中的甘氨酸位置通常不形成堆积空隙。这表明跨膜甘氨酸残基以类似于具有单跨膜螺旋的膜蛋白寡聚物中所见的方式介导多胞膜蛋白中的螺旋-螺旋相互作用。出现的图片是甘氨酸残基充当分子缺口，用于在折叠的蛋白质复合物中定向多个螺旋。
The nature and distribution of amino acids in the helix interfaces of four polytopic membrane proteins (cytochrome c oxidase, bacteriorhodopsin, the photosynthetic reaction center of Rhodobacter sphaeroides, and the potassium channel of Streptomyces lividans) are studied to address the role of glycine in transmembrane helix packing. In contrast to soluble proteins where glycine is a noted helix breaker, the backbone dihedral angles of glycine in transmembrane helices largely fall in the standard a-helical region of a Ramachandran plot. An analysis of helix packing reveals that glycine residues in the transmembrane region of these proteins are predominantly oriented toward helix-helix interfaces and have a high occurrence at helix crossing points. Moreover, packing Voids are generally not formed at the position of glycine in folded protein structures. This suggests that transmembrane glycine residues mediate helix-helix interactions in polytopic membrane proteins in a fashion similar to that seen in oligomers of membrane proteins with single membrane-spanning helices. The picture that emerges is one where glycine residues serve as molecular notches for orienting multiple helices in a folded protein complex.