Conformation of Spider Silk Proteins In Situ in the Intact Major Ampullate Gland and in Solution

Lefèvre, Thierry; Leclerc, Jérémie; Rioux-Dubé, Jean-François; Buffeteau, Thierry; Paquin, Marie-Claude; Rousseau, Marie‐Eve; Cloutier, Isabelle; Auger, Michèle; Gagné, Stéphane M.; Boudreault, Simon; Cloutier, Conrad; Pézolet, Michel

doi:10.1021/bm7005517

Cited by 66 publications

(102 citation statements)

References 22 publications

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“…The spidroin remains unassembled and predominantly contains helical shapes (α-helices, turns and 3 10 -helices), as observed in the deconvolution of Raman spectra. 10,56 Our simulations show that helices towards the beginning of the sequence are typically arranged at a ca. 60 degree angle to one another.…”

Section: Size Dependence Of Structural Transition and Shear Stressmentioning

confidence: 80%

“…[9][10][11] None of the spinning dopes were found to possess silk in β-sheet conformation. The presence of α-helices and left handed 3 10 -helices were identified by Raman microspectrophotmetry, 10 with NMR studies in contrast suggesting the silk is stored in a random coil state. 11 The MaSp sequences were shown to have no natural propensity for aggregation to give β-amyloid structures, a property of importance for silks in biomedical applications.…”

Section: Figure1amentioning

confidence: 99%

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Secondary Structure Transition and Critical Stress for a Model of Spider Silk Assembly

2016

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Spiders spin their silk from an aqueous solution to a solid fiber in ambient conditions. However, to date the assembly mechanism in the spider silk gland has not been satisfactorily explained. In this paper, we use molecular dynamics simulations to model N. clavipes MaSp1 dragline silk formation under shear flow and determine the secondary structure transitions leading to the experimentally observed fiber structures. While no experiments are performed on the silk fiber itself, insights from this polypeptide model can be transferred to the fiber scale. The novelty of this study lies in the calculation of the shear stress (300-700 MPa) required for fiber formation and identification of the amino acid residues involved in the transition. This is the first time that the shear stress has been quantified in connection with a secondary structure transition. By study of molecules containing varying numbers of contiguous MaSp1 repeats we identified the smallest molecule size that gives rise to a 'silk-like' structure contains six poly-alanine repeats.Through a probability analysis of the secondary structure we identify specific amino acids that transition from α-helix to β-sheet. In addition to portions of the poly-alanine section these amino acids include glycine, leucine and glutamine. Stability of β-sheet structures appears to arise from a close proximity in space of helices in the initial spidroin state. Our results are in agreement with the forces exerted by spiders in the silking process and the experimentally determined global secondary structure of spidroin and pulled MaSp1 silk. Our study emphasizes the role of shear in the assembly process of silk and can guide the design of microfluidic devices that attempt to mimic the natural spinning process and predict molecular requirements for the next generation of silk-based functional materials.

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Section: Size Dependence Of Structural Transition and Shear Stressmentioning

confidence: 80%

Section: Figure1amentioning

confidence: 99%

Secondary Structure Transition and Critical Stress for a Model of Spider Silk Assembly

2016

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“…Taking into consideration that repetitive amino acid sequences are unlikely to adopt an ideal random conformation without any (at least locally) regular structure,45 it would be plausible that PAS polypeptides show a kind of random‐coil structure influenced by the PPII conformation 46. Of note, it has been proposed that the PPII conformation represents the energetically most favored conformation of the peptide bond,47 since solvation of the hydrophilic polypeptide backbone is maximized while putative entropy loss due to formation of secondary structure with more pronounced order (such as α‐helix) is kept minimal.…”

Section: Resultsmentioning

confidence: 99%

The polypeptide biophysics of proline/alanine‐rich sequences (PAS): Recombinant biopolymers with PEG‐like properties

Breibeck

Skerra

2017

Biopolymers

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PAS polypeptides comprise long repetitive sequences of the small L‐amino acids proline, alanine and/or serine that were developed to expand the hydrodynamic volume of conjugated pharmaceuticals and prolong their plasma half‐life by retarding kidney filtration. Here, we have characterized the polymer properties both of the free polypeptides and in fusion with the biopharmaceutical IL‐1Ra. Data from size exclusion chromatography, dynamic light scattering, circular dichroism spectroscopy and quantification of hydrodynamic and polar properties demonstrate that the biosynthetic PAS polypeptides exhibit random coil behavior in aqueous solution astonishingly similar to the chemical polymer poly‐ethylene glycol (PEG). The solvent‐exposed PAS peptide groups, in the absence of secondary structure, account for strong hydrophilicity, with negligible contribution by the Ser side chains. Notably, PAS polypeptides exceed PEG of comparable molecular mass in hydrophilicity and hydrodynamic volume while exhibiting lower viscosity. Their uniform monodisperse composition as genetically encoded polymers and their biological nature, offering biodegradability, render PAS polypeptides a promising PEG mimetic for biopharmaceutical applications.

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“…Vibrational circular dichroism and NMR spectroscopy have further shown that the proteins adopt polyproline II (PPII), random coil and a-helix conformations. 72 The Protein Transformation During the Spinning Process in the Ma Gland…”

Section: Structure Of Silk By Raman Spectromicroscopymentioning

confidence: 99%

“…72 The spectrum of FIGURE 8 XX and ZZ polarized spectra of the spinning dope at different locations along the Ma duct's canal of N. clavipes. The probed points are specified with green arrows.…”

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Structure of silk by raman spectromicroscopy: From the spinning glands to the fibers

et al. 2011

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Raman spectroscopy has long been proved to be a useful tool to study the conformation of protein‐based materials such as silk. Thanks to recent developments, linearly polarized Raman spectromicroscopy has appeared very efficient to characterize the molecular structure of native single silk fibers and spinning dopes because it can provide information relative to the protein secondary structure, molecular orientation, and amino acid composition. This review will describe recent advances in the study of the structure of silk by Raman spectromicroscopy. A particular emphasis is put on the spider dragline and silkworm cocoon threads, other fibers spun by orb‐weaving spiders, the spinning dope contained in their silk glands and the effect of mechanical deformation. Taken together, the results of the literature show that Raman spectromicroscopy is particularly efficient to investigate all aspects of silk structure and production. The data provided can lead to a better understanding of the structure of the silk dope, transformations occurring during the spinning process, and structure and mechanical properties of native fibers. © 2011 Wiley Periodicals, Inc. Biopolymers 97: 322–336, 2012.

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Conformation of Spider Silk Proteins In Situ in the Intact Major Ampullate Gland and in Solution

Cited by 66 publications

References 22 publications

Secondary Structure Transition and Critical Stress for a Model of Spider Silk Assembly

Secondary Structure Transition and Critical Stress for a Model of Spider Silk Assembly

The polypeptide biophysics of proline/alanine‐rich sequences (PAS): Recombinant biopolymers with PEG‐like properties

Structure of silk by raman spectromicroscopy: From the spinning glands to the fibers

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