Chaw Ro Crystal, Saski Christopher A, Hayashi Cheryl Y
Department of Biology, University of California, Riverside, 900 University Ave., Riverside, 92521 CA, USA.
Clemson University Genomics and Computational Biology Facility, Institute for Translational Genomics, Biosystems Research Complex #310, 105 Collings St., Clemson, 29634 SC, USA.
Insect Biochem Mol Biol. 2017 Feb;81:80-90. doi: 10.1016/j.ibmb.2017.01.002. Epub 2017 Jan 2.
Spiders use a myriad of silk types for daily survival, and each silk type has a unique suite of task-specific mechanical properties. Of all spider silk types, pyriform silk is distinct because it is a combination of a dry protein fiber and wet glue. Pyriform silk fibers are coated with wet cement and extruded into "attachment discs" that adhere silks to each other and to substrates. The mechanical properties of spider silk types are linked to the primary and higher-level structures of spider silk proteins (spidroins). Spidroins are often enormous molecules (>250 kDa) and have a lengthy repetitive region that is flanked by relatively short (∼100 amino acids), non-repetitive amino- and carboxyl-terminal regions. The amino acid sequence motifs in the repetitive region vary greatly between spidroin type, while motif length and number underlie the remarkable mechanical properties of spider silk fibers. Existing knowledge of pyriform spidroins is fragmented, making it difficult to define links between the structure and function of pyriform spidroins. Here, we present the full-length sequence of the gene encoding pyriform spidroin 1 (PySp1) from the silver garden spider Argiope argentata. The predicted protein is similar to previously reported PySp1 sequences but the A. argentata PySp1 has a uniquely long and repetitive "linker", which bridges the amino-terminal and repetitive regions. Predictions of the hydrophobicity and secondary structure of A. argentata PySp1 identify regions important to protein self-assembly. Analysis of the full complement of A. argentata PySp1 repeats reveals extreme intragenic homogenization, and comparison of A. argentata PySp1 repeats with other PySp1 sequences identifies variability in two sub-repetitive expansion regions. Overall, the full-length A. argentata PySp1 sequence provides new evidence for understanding how pyriform spidroins contribute to the properties of pyriform silk fibers.
蜘蛛利用多种类型的蛛丝维持日常生存，且每种蛛丝都具有一套独特的、针对特定任务的机械性能。在所有蜘蛛丝类型中，梨形丝独具特色，因为它是干燥的蛋白质纤维与湿胶水的结合体。梨形丝纤维表面覆盖着湿水泥，并被挤压成“附着盘”，使蛛丝相互粘连以及与底物粘连。蜘蛛丝类型的机械性能与蜘蛛丝蛋白（蛛丝蛋白）的一级结构和高级结构相关。蛛丝蛋白通常是巨大的分子（>250 kDa），具有一个冗长的重复区域，其两侧是相对较短（约100个氨基酸）的非重复氨基末端和羧基末端区域。不同类型的蛛丝蛋白，其重复区域中的氨基酸序列基序差异很大，而基序的长度和数量则构成了蜘蛛丝纤维卓越机械性能的基础。目前关于梨形蛛丝蛋白的知识支离破碎，难以确定梨形蛛丝蛋白的结构与功能之间的联系。在此，我们展示了银腹园蛛（Argiope argentata）中编码梨形蛛丝蛋白1（PySp1）的基因的全长序列。预测的蛋白质与先前报道的PySp1序列相似，但银腹园蛛的PySp1具有独特的长且重复的“连接子”，它连接氨基末端和重复区域。对银腹园蛛PySp1的疏水性和二级结构的预测确定了对蛋白质自组装重要的区域。对银腹园蛛PySp1重复序列的完整互补分析揭示了极端的基因内同质化，并且将银腹园蛛PySp1重复序列与其他PySp1序列进行比较，确定了两个亚重复扩展区域的变异性。总体而言，银腹园蛛PySp1的全长序列为理解梨形蛛丝蛋白如何影响梨形丝纤维的性能提供了新证据。
