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Int. J. Mol. Sci. 2016, 17(8), 1305; doi:10.3390/ijms17081305

Characterizing Aciniform Silk Repetitive Domain Backbone Dynamics and Hydrodynamic Modularity

1
Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS B3H 4R2, Canada
2
Department of Chemistry, Dalhousie University, Halifax, NS B3H 4R2, Canada
*
Author to whom correspondence should be addressed.
Academic Editor: John G. Hardy
Received: 29 June 2016 / Revised: 3 August 2016 / Accepted: 4 August 2016 / Published: 10 August 2016
(This article belongs to the Special Issue Silk-Based Materials: From Production to Characterization)
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Abstract

Spider aciniform (wrapping) silk is a remarkable fibrillar biomaterial with outstanding mechanical properties. It is a modular protein consisting, in Argiope trifasciata, of a core repetitive domain of 200 amino acid units (W units). In solution, the W units comprise a globular folded core, with five α-helices, and disordered tails that are linked to form a ~63-residue intrinsically disordered linker in concatemers. Herein, we present nuclear magnetic resonance (NMR) spectroscopy-based 15N spin relaxation analysis, allowing characterization of backbone dynamics as a function of residue on the ps–ns timescale in the context of the single W unit (W1) and the two unit concatemer (W2). Unambiguous mapping of backbone dynamics throughout W2 was made possible by segmental NMR active isotope-enrichment through split intein-mediated trans-splicing. Spectral density mapping for W1 and W2 reveals a striking disparity in dynamics between the folded core and the disordered linker and tail regions. These data are also consistent with rotational diffusion behaviour where each globular domain tumbles almost independently of its neighbour. At a localized level, helix 5 exhibits elevated high frequency dynamics relative to the proximal helix 4, supporting a model of fibrillogenesis where this helix unfolds as part of the transition to a mixed α-helix/β-sheet fibre. View Full-Text
Keywords: aciniform spidroin (AcSp1); wrapping silk; recombinant spider silk; modular proteins; reduced spectral density mapping; hydrodynamics characterization; nuclear magnetic resonance spectroscopy; split intein; segmental-labelling aciniform spidroin (AcSp1); wrapping silk; recombinant spider silk; modular proteins; reduced spectral density mapping; hydrodynamics characterization; nuclear magnetic resonance spectroscopy; split intein; segmental-labelling
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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

Tremblay, M.-L.; Xu, L.; Sarker, M.; Liu, X.-Q.; Rainey, J.K. Characterizing Aciniform Silk Repetitive Domain Backbone Dynamics and Hydrodynamic Modularity. Int. J. Mol. Sci. 2016, 17, 1305.

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