title: Structure of model peptides based on Nephila clavipes dragline silk spidroin (MaSp1) studied by 13C cross polarization/magic angle spinning NMR.
abstract: To obtain detailed structural information for spider dragline spidroin (MaSp1), we prepared three versions of the consensus peptide GGLGGQGAGAAAAAAGGAGQGGYGGLGSQGAGR labeled with 13C at six different sites. The 13C CP/MAS NMR spectra were observed after treating the peptides with different reagents known to alter silk protein conformations. The conformation-dependent 13C NMR chemical shifts and peak deconvolution were used to determine the local structure and the fractional compositions of the conformations, respectively. After trifluoroacetic acid (solvent)/diethyl ether (coagulant) treatment, the N-terminal region of poly-Ala (PLA) sequence, Ala8 and Ala10, adopted predominantly the alpha-helix with a substantial amount of beta-sheet. The central region, Ala15, Ala18, and Leu26, and C-terminal region, Ala31, of the peptide were dominated by either 3(1)-helix or alpha-helix. There was no indication of beta-sheet, although peak broadening indicates that the torsion angle distribution is relatively large. After 9 M LiBr/dialysis treatment, three kinds of conformation, beta-sheet, random coil, and 3(1)-helix, appeared, in almost equal amounts of beta-sheet and random coil conformations for Ala8 and Ala10 residues and distorted 3(1)-helix at the central region of the peptide. In contrast, after formic acid/methanol and 8 M urea/acetonitrile treatments, all of the local structure tends to beta-sheet, although small amounts of random coil are also observed. The peak pattern of the Ala Cbeta carbon after 8 M urea/acetonitrile treatment is similar to the corresponding patterns of silk fiber from Bombyx mori and Samia cynthia ricini. We also synthesized a longer 13C-labeled peptide containing two PLA blocks and three Gly-rich blocks. After 8 M urea/acetonitrile treatment, the conformation pattern was closely similar to that of the shorter peptide.
authors.affiliation: Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan.
authors.forename: Mingying
authors.initials: M
authors.lastname: Yang
authors.forename: Yasumoto
authors.initials: Y
authors.lastname: Nakazawa
authors.forename: Kazuo
authors.initials: K
authors.lastname: Yamauchi
authors.forename: David
authors.initials: D
authors.lastname: Knight
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Asakura
mesh_terms: D000097:Acetonitriles / Q000737:chemistry; D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001672:Biocompatible Materials / Q000737:chemistry; D002244:Carbon / Q000737:chemistry; D002250:Carbon Radioisotopes / Q000494:pharmacology; D005349:Fibroins / Q000737:chemistry*; D005998:Glycine / Q000737:chemistry; D019476:Insect Proteins / Q000737:chemistry*; D007930:Leucine / Q000737:chemistry; D008027:Light; D046911:Macromolecular Substances / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D000432:Methanol / Q000737:chemistry; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D047011:Silk / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D013112:Spiders; D014269:Trifluoroacetic Acid / Q000494:pharmacology; D014508:Urea / Q000494:pharmacology
chemical_list: D000097:Acetonitriles; D001672:Biocompatible Materials; D002250:Carbon Radioisotopes; D019476:Insect Proteins; D046911:Macromolecular Substances; D010455:Peptides; D047011:Silk; D012997:Solvents; C086087:spidroin 1; D002244:Carbon; D014508:Urea; D005349:Fibroins; D014269:Trifluoroacetic Acid; D007930:Leucine; D000409:Alanine; D005998:Glycine; D000432:Methanol; C032159:acetonitrile