title: Structural Model for the Spider Silk Protein Spidroin-1.
abstract: Most reports about the 3-D structure of spidroin-1 have been proposed for the protein in solid state or for individual domains of these proteins. A gel-based mass spectrometry strategy using collision-induced dissociation (CID) and electron-transfer dissociation (ETD) fragmentation methods was used to completely sequence spidroins-1A and -1B and to assign a series of post-translational modifications (PTMs) on to the spidroin sequences. A total of 15 and 16 phosphorylation sites were detected on spidroin-1A and -1B, respectively. In this work, we present the nearly complete amino acid sequence of spidroin-1A and -1B, including the nonrepetitive N- and C-terminal domains and a highly repetitive central core. We also described a fatty acid layer surrounding the protein fibers and PTMs in the sequences of spidroin-1A and -1B, including phosphorylation. Thus, molecular models for phosphorylated spidroins were proposed in the presence of a mixture fatty acids/water (1:1) and submitted to molecular dynamics simulation. The resulting models presented high content of coils, a higher percentage of α-helix, and an almost neglected content of 310-helix than the previous models. Knowledge of the complete structure of spidroins-1A and -1B would help to explain the mechanical features of silk fibers. The results of the current investigation provide a foundation for biophysical studies of the mechanoelastic properties of web-silk proteins.
authors.affiliation: Center of the Study of Social Insects, Department of Biology, Institute of Biosciences of Rio Claro, São Paulo State University , Rio Claro, SP 13500, Brazil.|Department of Pediatrics, Medical University of Vienna , Vienna 1090, Austria.
authors.forename: José Roberto Aparecido
authors.initials: JR
authors.lastname: dos Santos-Pinto
authors.affiliation: Center of the Study of Social Insects, Department of Biology, Institute of Biosciences of Rio Claro, São Paulo State University , Rio Claro, SP 13500, Brazil.
authors.forename: Helen Andrade
authors.initials: HA
authors.lastname: Arcuri
authors.affiliation: Department of Paleontology, Geological Survey of Austria , Vienna 1230, Austria.
authors.forename: Helga
authors.initials: H
authors.lastname: Priewalder
authors.affiliation: Center of the Study of Social Insects, Department of Biology, Institute of Biosciences of Rio Claro, São Paulo State University , Rio Claro, SP 13500, Brazil.
authors.forename: Heliana Clara
authors.initials: HC
authors.lastname: Salles
authors.affiliation: Center of the Study of Social Insects, Department of Biology, Institute of Biosciences of Rio Claro, São Paulo State University , Rio Claro, SP 13500, Brazil.
authors.forename: Mario Sergio
authors.initials: MS
authors.lastname: Palma
authors.affiliation: Department of Pediatrics, Medical University of Vienna , Vienna 1090, Austria.
authors.forename: Gert
authors.initials: G
authors.lastname: Lubec
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D005349:Fibroins / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D047011:Silk / Q000737:chemistry*; D013112:Spiders / Q000737:chemistry*
chemical_list: D047011:Silk; C086087:spidroin 1; D005349:Fibroins
keywords: Nephila clavipes; mass spectrometry; molecular dynamics; post-translational modification; silk proteins