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Tightly winding structure of sequential model peptide for repeated helical region in Samia cynthia ricini silk fibroin studied with solid‐state NMR
Author(s) -
Nakazawa Yasumoto,
Bamba Mie,
Nishio Satoko,
Asakura Tetsuo
Publication year - 2003
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.0239203
Subject(s) - fibroin , peptide , crystallography , silk , magic angle spinning , helix (gastropod) , solid state nuclear magnetic resonance , bombyx mori , chemistry , residue (chemistry) , alpha helix , stereochemistry , circular dichroism , materials science , nuclear magnetic resonance spectroscopy , nuclear magnetic resonance , physics , biology , biochemistry , ecology , snail , composite material , gene
There are many kinds of silks from silkworms and spiders with different structures and properties, and thus, silks are suitable to study the structure‐property relationship of fibrous proteins. Silk fibroin from a wild silkworm, Samia cynthia ricini , mainly consists of the repeated similar sequences by about 100 times where there are alternative appearances of the polyalanine (Ala) 12–13 region and the Gly‐rich region. In this paper, a sequential model peptide, GGAGGGYGGDGG(A) 12 GGAGDGYGAG, which is a typical sequence of the silk fibroin, was synthesized, and the atomic‐level conformations of Gly residues at the N‐ and C‐terminal ends of the polyalanine region were determined as well as that of the central Ala residue using 13 C 2D spin diffusion solid‐state nuclear magnetic resonance (NMR) under off‐magic angle spinning. In the model peptide with α‐helical conformation, the torsion angle of the central Ala residue, the 19th Ala, was determined to be (ϕ, ψ) = (−60°, −50°), which was a typical α‐helical structure, but the torsion angles of two Gly residues, the 12th and 25th Gly residues, which are located at the N‐ and C‐terminal ends of the polyalanine region, were determined to be (ϕ,ψ) = (−70°, −30°) and (ϕ,ψ) = (−70°, −20°), respectively. Thus, it was observed that the turns at both ends of polyalanine with α‐helix conformation in the model peptide are tightly wound.