title: Tightly winding structure of sequential model peptide for repeated helical region in Samia cynthia ricini silk fibroin studied with solid-state NMR.
abstract: 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 alpha-helical conformation, the torsion angle of the central Ala residue, the 19th Ala, was determined to be (phi, psi) = (-60 degrees, -50 degrees ), which was a typical alpha-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 (phi, psi) = (-70 degrees, -30 degrees ) and (phi, psi) = (-70 degrees, -20 degrees ), respectively. Thus, it was observed that the turns at both ends of polyalanine with alpha-helix conformation in the model peptide are tightly wound.
authors.affiliation: Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan.
authors.forename: Yasumoto
authors.initials: Y
authors.lastname: Nakazawa
authors.forename: Mie
authors.initials: M
authors.lastname: Bamba
authors.forename: Satoko
authors.initials: S
authors.lastname: Nishio
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Asakura
mesh_terms: D000409:Alanine / Q000378:metabolism; D000818:Animals; D012831:Bombyx / Q000737:chemistry*; D005998:Glycine / Q000378:metabolism; D019476:Insect Proteins / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D010455:Peptides / Q000737:chemistry*; D047011:Silk
chemical_list: D019476:Insect Proteins; D010455:Peptides; D047011:Silk; D000409:Alanine; D005998:Glycine