Analysis of repetitive amino acid motifs reveals the essential features of spider dragline silk proteins

PLoS One. 2017 Aug 23;12(8):e0183397. doi: 10.1371/journal.pone.0183397. eCollection 2017.

Abstract

The extraordinary mechanical properties of spider dragline silk are dependent on the highly repetitive sequences of the component proteins, major ampullate spidroin 1 and 2 (MaSp2 and MaSp2). MaSp sequences are dominated by repetitive modules composed of short amino acid motifs; however, the patterns of motif conservation through evolution and their relevance to silk characteristics are not well understood. We performed a systematic analysis of MaSp sequences encompassing infraorder Araneomorphae based on the conservation of explicitly defined motifs, with the aim of elucidating the essential elements of MaSp1 and MaSp2. The results show that the GGY motif is nearly ubiquitous in the two types of MaSp, while MaSp2 is invariably associated with GP and di-glutamine (QQ) motifs. Further analysis revealed an extended MaSp2 consensus sequence in family Araneidae, with implications for the classification of the archetypal spidroins ADF3 and ADF4. Additionally, the analysis of RNA-seq data showed the expression of a set of distinct MaSp-like variants in genus Tetragnatha. Finally, an apparent association was uncovered between web architecture and the abundance of GP, QQ, and GGY motifs in MaSp2, which suggests a co-expansion of these motifs in response to the evolution of spiders' prey capture strategy.

MeSH terms

  • Amino Acid Motifs*
  • Amino Acid Sequence
  • Animals
  • Conserved Sequence
  • Fibroins / chemistry*
  • Silk / chemistry*
  • Spiders

Substances

  • Silk
  • spidroin 1
  • spidroin 2
  • Fibroins

Grants and funding

This work was supported by Japan Science and Technology Agency (JST), grant: Impulsing Paradigm Change through Disruptive Technologies Program (ImPACT) (http://www.jst.go.jp/impact/en/index.html). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.