Correlation between protein secondary structure and mechanical performance for the ultra-tough dragline silk of Darwin's bark spider
Correlation between protein secondary structure and mechanical performance for the ultra-tough dragline silk of Darwin's bark spider
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DOI：
10.1098/rsif.2021.0320
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发表时间：
2021-06-16
影响因子：
3.9
通讯作者：
Dhinojwala, Ali
中科院分区：
文献类型：
--
作者：
Htut, K. Zin;Alicea-Serrano, Angela M.;Dhinojwala, Ali
蜘蛛主腹状丝（MA）具有高拉伸强度和延伸性，通常是MaSp1和MaSp2蛋白的混合物，后者含有促进延伸性和超收缩的甘氨酸-脯氨酸-甘氨酸-甘氨酸- x重复基序。据估计，达尔文吠蛛（Caerostris darwini）的MA丝比其他蜘蛛种类的MA丝坚韧两到三倍。先前的研究表明，一种独特的MaSp4蛋白将脯氨酸整合到一个新的甘氨酸-脯氨酸-甘氨酸-脯氨酸基序中，这可能解释了C. darwin MA丝绸非凡的韧性。然而，对于C. darwin来说，蛛丝的分子结构与其机械性能之间并没有直接的联系。本研究将C. darwin和其他四种蜘蛛MA丝的相对蛋白质二级结构组成与超收缩前后的力学性能进行了关联，以了解额外的MaSp4蛋白的影响。我们的研究结果表明，C. darwin MA蚕丝具有独特的蛋白质组成，其螺旋（31%）和β -片（20%）的比例低于其他物种。在超收缩之前，韧性、模量和抗拉强度与β -片、无序或随机卷曲区域和β -匝数的百分比相关。然而，在超收缩后，只有模量和断裂应变与β -片数和β -匝数的百分比相关。我们的研究强调，要建立完整的结构-性能相关模型，还需要包括晶体尺寸、晶体和链取向在内的额外信息。
The spider major ampullate (MA) silk exhibits high tensile strength and extensibility and is typically a blend of MaSp1 and MaSp2 proteins with the latter comprising glycine-proline-glycine-glycine-X repeating motifs that promote extensibility and supercontraction. The MA silk from Darwin's bark spider (Caerostris darwini) is estimated to be two to three times tougher than the MA silk from other spider species. Previous research suggests that a unique MaSp4 protein incorporates proline into a novel glycine-proline-glycine-proline motif and may explain C. darwini MA silk's extraordinary toughness. However, no direct correlation has been made between the silk's molecular structure and its mechanical properties for C. darwini. Here, we correlate the relative protein secondary structure composition of MA silk from C. darwini and four other spider species with mechanical properties before and after supercontraction to understand the effect of the additional MaSp4 protein. Our results demonstrate that C. darwini MA silk possesses a unique protein composition with a lower ratio of helices (31%) and beta -sheets (20%) than other species. Before supercontraction, toughness, modulus and tensile strength correlate with percentages of beta -sheets, unordered or random coiled regions and beta -turns. However, after supercontraction, only modulus and strain at break correlate with percentages of beta -sheets and beta -turns. Our study highlights that additional information including crystal size and crystal and chain orientation is necessary to build a complete structure-property correlation model.