title: 13 C solid-state NMR study of the 13 C-labeled peptide, (E)8 GGLGGQGAG(A)6 GGAGQGGYGG as a model for the local structure of Nephila clavipes dragline silk (MaSp1) before and after spinning.
abstract: We prepared the water soluble model peptide, (E)(8) GGLGGQGAG(A)(6) GGAGQGGYGG, to throw light on the local structure of spidroin 1 (MaSpl) protein in spider dragline silk of Nephila clavipes before and after spinning. Solution (13) C NMR showed that the conformation of the peptide in aqueous solution was essentially random coil. Solid-state NMR was used to follow conformation-dependent (13) C chemical shifts in (13) C selectively labeled versions of the peptide. The peptide lyophilized from an aqueous solution at neutral pH (hereafter referred to as "without acid treatment)"was used to mimic the state of the spidroin stored in the spider's silk gland while the peptide precipitated from the acidic solution ("with acid treatment") was used to simulate the role of acid treatment in inducing conformation change in the natural spinning process. In without acid treatment, the fraction of random coil conformation was lowest in the N-terminal region (residues 15-18) when compared with the C-terminus. The conformational change produced by the acid treatment occurred in the sequence, G(15) AG(A)(6) GGAG(27), interposed between pairs of Gly residues pairs, Gly(12,13), and Gly(29,30). The acid treated peptide showed a remarkable decrease in the fraction of random coil conformation from A(20) to A(23) in the poly-Ala region when compared with the peptide without acid treatment. These observations taken together suggest that the peptide can be used as a model for studying the localization of the conformation change in spider silk fibroin in the natural spinning and the role of acid treatment in this process.
authors.affiliation: Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Yazawa
authors.forename: Erika
authors.initials: E
authors.lastname: Yamaguchi
authors.forename: David
authors.initials: D
authors.lastname: Knight
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Asakura
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002247:Carbon Isotopes; D005998:Glycine / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008969:Molecular Sequence Data; D010455:Peptides / Q000032:analysis / Q000138:chemical synthesis*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D047011:Silk / Q000737:chemistry*; D012996:Solutions; D013112:Spiders / Q000502:physiology
chemical_list: D002247:Carbon Isotopes; D010455:Peptides; D047011:Silk; D012996:Solutions; D005998:Glycine