310-helix adjoining α-helix and β-strand:: Sequence and structural features and their conservation
310-helix adjoining α-helix and β-strand:: Sequence and structural features and their conservation
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DOI：
10.1002/bip.20266
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发表时间：
2005-06-15
期刊：
影响因子：
2.9
通讯作者：
Chakrabarti, P
中科院分区：
文献类型：
--
作者：
Pal, L;Dasgupta, B;Chakrabarti, P
a-螺旋末端的氨基酸使用是否会因环境而改变？当有一个相邻的3（10）-螺旋，可以一个单一的螺旋圆柱体包含合成螺旋？对已知蛋白质结构中分别发现的138例和107例3（10）-α和α-3（10）复合螺旋的分析表明，首先出现的二级结构元件将其特征强加于接下来出现的结构元件的序列。因此，当前面有3（10）-螺旋时，脯氨酸优先出现在所有α-螺旋的N1位置，转移到N2位置，这是3（10）-螺旋C-末端加帽的典型特征。当α-或3（10）-螺旋引入另一种类型的螺旋时，在连接处有一个弯曲，特别是对于3（10）-α复合物，两个连接残基面向内并埋在结构内。因此，单个螺旋圆柱体可能不能正确地表示复合螺旋，弯曲为三级结构提供了呈现球形形状的手段，非常类似于脯氨酸诱导的扭结对α-螺旋的作用。β-3（10）和3（10）-β复合物出现的三级结构背景可能不同，导致两种情况下二级结构元件之间的角度不同。3（10）-螺旋和β-链的复合物在同源结构家族的成员中比两种类型的螺旋之间的复合物保守得多;在许多前一种情况下，3（10）-螺旋构成β-发夹或β-β-角基序中的环。链的整体折叠可能比复合物中二级结构元件的实际鉴定更保守。(c)2005 Wiley Periodicals，Inc.
Does the amino acid use at the terminal positions of an a-helix become altered depending on the context-more specifically. when there is an adjoining 3(10)-helix, and can a single helical cylinder encompass the resultant composite helix? An analysis of 138 and 107 cases of 3(10)-alpha and alpha-3(10) composite helices, respectively,found in known protein structures indicate that the secondary structural element occurring first imposes its characteristics on the sequence of the structural element coming next. Thus, when preceded by a 3(10)-helix, the preference of proline to occur at the N1 position of all alpha-helix is shifted to the N2 position, a typical characteristic of the C-terminal capping of the 3(10)-helix. When an alpha- or a 3(10)-helix leads into a helix of the other type, there is a bend at the junction, especiaily for the 3(10)-alpha composite, with the two junction residues facing inward and buried within the structure. Thus a single helical cylinder may not properly represent a composite helix, the bend providing a means for the tertiary structure to assume a globular shape, very much akin to what a proline-induced kink does to an alpha-helix. The tertiary structural context in which beta-3(10) and 3(10)-beta composites occurs can be different, causing the angle between the secondary structural elements in the two cases to be different. Composites of 3(10)-helices and beta-strands are much more conserved among members in families of homologous structures than those between two types of helices; in many of the former instances, the 3(10)-helix constitutes the loops in beta-hairpin or beta-beta-corner motifs. The overall fold of the chain may be more conserved than the actual identify of the secondary, structure elements in a composite. (c) 2005 Wiley Periodicals, Inc.