Title: Structure Determination of a Peptide Model of the Repeated Helical Domain in <i>Samia </i><i>c</i><i>ynthia </i><i>r</i><i>icini</i> Silk Fibroin before Spinning by a Combination of Advanced Solid-State NMR Methods
Abstract: Fibrous proteins unlike globular proteins, contain repetitive amino acid sequences, giving rise to very regular secondary protein structures. Silk fibroin from a wild silkworm, Samia cynthia ricini, consists of about 100 repeats of alternating polyalanine (poly-Ala) regions of 12−13 residues in length and Gly-rich regions. In this paper, the precise structure of the model peptide, GGAGGGYGGDGG(A)12GGAGDGYGAG, which is a typical repeated sequence of the silk fibroin, was determined using a combination of three kinds of solid-state NMR studies; a quantitative use of 13C CP/MAS NMR chemical shift with conformation-dependent 13C chemical shift contour plots, 2D spin diffusion 13C solid-state NMR under off magic angle spinning and rotational echo double resonance. The structure of the model peptide corresponding to the silk fibroin structure before spinning was determined. The torsion angles of the central Ala residue, Ala19, in the poly-Ala region were determined to be (φ, ψ) = (−59°, −48°) which are values typically associated with α-helical structures. However, the torsion angles of the Gly25 residue adjacent to the C-terminal side of the poly-Ala chain were determined to be (φ, ψ) = (−66°, −22°) and those of Gly12 and Ala13 residues at the N-terminal of the poly-Ala chain to be (φ, ψ) = (−70°, −30°). In addition, REDOR experiments indicate that the torsion angles of the two C-terminal Ala residues, Ala23 and Ala24, are (φ, ψ) = (−66°, −22°) and those of N-terminal two Ala residues, Ala13 and Ala14 are (φ, ψ) = (−70°, −30°). Thus, the local structure of N-terminal and C-terminal residues, and also the neighboring residues of α-helical poly-Ala chain in the model peptide is a more strongly wound structure than found in typical α-helix structures.
Publication Year: 2003
Publication Date: 2003-05-21
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 70
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