Department of Biology, University of California Riverside, Riverside, California, United States of America.
PLoS One. 2007 Jun 13;2(6):e514. doi: 10.1371/journal.pone.0000514.
Spider dragline (major ampullate) silk outperforms virtually all other natural and manmade materials in terms of tensile strength and toughness. For this reason, the mass-production of artificial spider silks through transgenic technologies has been a major goal of biomimetics research. Although all known arthropod silk proteins are extremely large (>200 kiloDaltons), recombinant spider silks have been designed from short and incomplete cDNAs, the only available sequences. Here we describe the first full-length spider silk gene sequences and their flanking regions. These genes encode the MaSp1 and MaSp2 proteins that compose the black widow's high-performance dragline silk. Each gene includes a single enormous exon (>9000 base pairs) that translates into a highly repetitive polypeptide. Patterns of variation among sequence repeats at the amino acid and nucleotide levels indicate that the interaction of selection, intergenic recombination, and intragenic recombination governs the evolution of these highly unusual, modular proteins. Phylogenetic footprinting revealed putative regulatory elements in non-coding flanking sequences. Conservation of both upstream and downstream flanking sequences was especially striking between the two paralogous black widow major ampullate silk genes. Because these genes are co-expressed within the same silk gland, there may have been selection for similarity in regulatory regions. Our new data provide complete templates for synthesis of recombinant silk proteins that significantly improve the degree to which artificial silks mimic natural spider dragline fibers.
蜘蛛牵引丝（主要囊状）在拉伸强度和韧性方面优于几乎所有其他天然和人造材料。出于这个原因，通过转基因技术大规模生产人工蜘蛛丝一直是仿生学研究的主要目标。尽管所有已知的节肢动物丝蛋白都非常大（>200 千道尔顿），但重组蜘蛛丝是由短而不完整的 cDNA 设计而成的，这是唯一可用的序列。在这里，我们描述了第一个全长蜘蛛丝基因序列及其侧翼区域。这些基因编码构成黑寡妇高性能牵引丝的 MaSp1 和 MaSp2 蛋白。每个基因都包含一个单一的巨大外显子（>9000 个碱基对），翻译成高度重复的多肽。氨基酸和核苷酸水平上序列重复的变异模式表明，选择、基因间重组和基因内重组的相互作用控制着这些非常不寻常的模块化蛋白的进化。系统发育足迹分析揭示了非编码侧翼序列中的推定调节元件。两个平行的黑寡妇主要囊状丝基因之间的上下游侧翼序列的保守性尤其引人注目。由于这些基因在同一个丝腺中共表达，因此在调节区域可能存在相似性的选择。我们的新数据为合成重组丝蛋白提供了完整的模板，这些模板显著提高了人工丝模仿天然蜘蛛牵引丝纤维的程度。
