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首页> 外文期刊>Journal of Molecular Biology >Evidence from flagelliform silk cDNA for the structural basis of elasticity and modular nature of spider silks
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Evidence from flagelliform silk cDNA for the structural basis of elasticity and modular nature of spider silks

机译：鞭毛状丝cDNA为蜘蛛丝弹性和模块化性质的结构基础提供的证据

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Orb-web weaving spiders rely on their aerial nets to entrap flying prey. A key mechanical feature of orb-web design is the high elasticity of the capture spiral. We report the cloning of substantial cDNA for flagelliform gland silk protein, which forms the core fiber of the catching spiral. Like all silks, the flagelliform protein is composed largely of iterated sequences. The dominant repeat of this protein is Gly-Pro-Gly-Gly-X, which can appear up to 63 times in tandem arrays. This motif likely forms Pro(2)-Gly(3) type II beta-turns and the resulting series of concatenated beta-turns are thought to form a beta-spiral. We propose that this spring-like helix is the basis for the elasticity of silk. The variable fifth position of the motif (X) is occupied by a small subset of residues (Ala, Ser, Tyr, Val). Moreover, these X amino acids occur in specific patterns throughout the repeats. This ordered variation strongly suggests that with hydration, the beta-spirals form hydrogen-bonded networks that increase the elasticity of flagelliform silk. The self-assembly of flagelliform protein monomers into silk fibers may be promoted by beta-spiral/beta-spiral interactions. Additionally, the other two motifs in the flagelliform protein, Gly-Gly-X and a spacer that disrupts the glycine-rich regions, may contribute to the alignment of monomers into fibers. The flagelliform protein cDNA was compared to the other members of the spider silk gene family. We show that all spider silk proteins can be characterized as sets of shared structural modules. The occurrence of these modules among the proteins is inconsistent with the phylogenetic relationships inferred from the C-terminal regions. This observation, along with the high level of variation among individual flagelliform protein repeats, but striking lack of such variation in the other silk proteins, suggests that unusual homogenization processes are involved in silk protein evolution. (C) 1998 Academic Press Limited. [References: 46]
机译：球网织蜘蛛依靠它们的空中网来捕获飞行的猎物。球网设计的关键机械特征是捕获螺旋的高弹性。我们报告了鞭毛状腺丝蛋白的实质cDNA的克隆，该蛋白形成了捕获螺旋的核心纤维。像所有的丝绸一样，鞭毛蛋白主要由重复序列组成。该蛋白的主要重复序列是Gly-Pro-Gly-Gly-X，在串联排列中最多可出现63次。此母题可能会形成Pro（2）-Gly（3）II型β-转角，并且所产生的一系列串联的β-转角被认为形成了β-螺旋。我们建议，这种像弹簧一样的螺旋线是丝绸弹性的基础。基序（X）的可变第五位置被一小部分残基（Ala，Ser，Tyr，Val）占据。而且，这些X氨基酸在整个重复过程中以特定模式出现。这种有序的变化强烈表明，水合后，β-螺旋形成氢键网络，从而增加了鞭毛状丝的弹性。 β-螺旋/β-螺旋相互作用可促进鞭毛状蛋白质单体自组装成丝纤维。此外，鞭毛蛋白中的其他两个基序Gly-Gly-X和可破坏富含甘氨酸区域的间隔基可能有助于单体排列成纤维。将鞭毛蛋白cDNA与蜘蛛丝基因家族的其他成员进行比较。我们表明，所有蜘蛛丝蛋白都可以表征为一组共享的结构模块。这些模块在蛋白质中的出现与从C端区域推断出的系统发育关系不一致。该观察结果以及各个鞭毛蛋白重复序列​​之间的高度变异，但其他丝蛋白中却缺乏这种变异，这表明丝蛋白进化涉及异常的均质化过程。 （C）1998 Academic Press Limited。 [参考：46]

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