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Int. J. Mol. Sci. 2016, 17(8), 1294; doi:10.3390/ijms17081294

Evidence of Decoupling Protein Structure from Spidroin Expression in Spider Dragline Silks

1
Evolution & Ecology Research Centre, School of Biological, Earth & Environmental Sciences, University of New South Wales, Sydney 2052, Australia
2
Department of Life Science, Tunghai University, Taichung 40704, Taiwan
3
Graduate School of Biomedical Engineering, University of New South Wales, Sydney 2052, Australia
4
NMR Facility, Mark Wainwright Analytical Centre, University of New South Wales, Sydney 2052, Australia
*
Author to whom correspondence should be addressed.
Academic Editor: John G. Hardy
Received: 30 June 2016 / Revised: 28 July 2016 / Accepted: 1 August 2016 / Published: 9 August 2016
(This article belongs to the Special Issue Silk-Based Materials: From Production to Characterization)
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Abstract

The exceptional strength and extensibility of spider dragline silk have been thought to be facilitated by two spidroins, major ampullate spidroin 1 (MaSp1) and major ampullate spidroin 2 (MaSp2), under the assumption that protein secondary structures are coupled with the expressed spidroins. We tested this assumption for the dragline silk of three co-existing Australian spiders, Argiope keyserlingi, Latrodectus hasselti and Nephila plumipes. We found that silk amino acid compositions did not differ among spiders collected in May. We extended these analyses temporally and found the amino acid compositions of A. keyserlingi silks to differ when collected in May compared to November, while those of L. hasselti did not. To ascertain whether their secondary structures were decoupled from spidroin expression, we performed solid-state nuclear magnetic resonance spectroscopy (NMR) analysis on the silks of all spiders collected in May. We found the distribution of alanine toward β-sheet and 3,10helix/random coil conformations differed between species, as did their relative crystallinities, with A. keyserlingi having the greatest 3,10helix/random coil composition and N. plumipes the greatest crystallinity. The protein secondary structures correlated with the mechanical properties for each of the silks better than the amino acid compositions. Our findings suggested that a differential distribution of alanine during spinning could decouple secondary structures from spidroin expression ensuring that silks of desirable mechanical properties are consistently produced. Alternative explanations include the possibility that other spidroins were incorporated into some silks. View Full-Text
Keywords: amino acids; high performance liquid chromatography; mechanical properties; orb weaving spiders; protein secondary structures; silk spinning; solid-state nuclear magnetic resonance spectroscopy amino acids; high performance liquid chromatography; mechanical properties; orb weaving spiders; protein secondary structures; silk spinning; solid-state nuclear magnetic resonance spectroscopy
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Blamires, S.J.; Kasumovic, M.M.; Tso, I.-M.; Martens, P.J.; Hook, J.M.; Rawal, A. Evidence of Decoupling Protein Structure from Spidroin Expression in Spider Dragline Silks. Int. J. Mol. Sci. 2016, 17, 1294.

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