title: Characterizing Aciniform Silk Repetitive Domain Backbone Dynamics and Hydrodynamic Modularity.
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 (15)N 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.
authors: Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS B3H 4R2, Canada. mltremblay@dal.ca.
authors: Marie-Laurence
authors: ML
authors: Tremblay
authors: Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS B3H 4R2, Canada. ln217415@dal.ca.
authors: Lingling
authors: L
authors: Xu
authors: Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS B3H 4R2, Canada. muzaddid.sarker@dal.ca.
authors: Muzaddid
authors: M
authors: Sarker
authors: Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS B3H 4R2, Canada. paul.liu@dal.ca.
authors: Xiang-Qin
authors: XQ
authors: Liu
authors: Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS B3H 4R2, Canada. jan.rainey@dal.ca.|Department of Chemistry, Dalhousie University, Halifax, NS B3H 4R2, Canada. jan.rainey@dal.ca.
authors: Jan K
authors: JK
authors: Rainey
mesh_terms: D000818:Animals; D019476:Insect Proteins / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D017433:Protein Structure, Secondary; D047011:Silk / Q000737:chemistry*; D013112:Spiders / Q000737:chemistry; D020040:Trans-Splicing
chemical_list: D019476:Insect Proteins; D047011:Silk
keywords: aciniform spidroin (AcSp1); hydrodynamics characterization; modular proteins; nuclear magnetic resonance spectroscopy; recombinant spider silk; reduced spectral density mapping; segmental-labelling; split intein; wrapping silk