title: Spider glue proteins have distinct architectures compared with traditional spidroin family members.
abstract: Adhesive spider glues are required to perform a variety of tasks, including web construction, prey capture, and locomotion. To date, little is known regarding the molecular and structural features of spider glue proteins, in particular bioadhesives that interconnect dragline or scaffolding silks during three-dimensional web construction. Here we use biochemical and structural approaches to identify and characterize two aggregate gland specific gene products, AgSF1 and AgSF2, and demonstrate that these proteins co-localize to the connection joints of both webs and wrapping silks spun from the black widow spider, Latrodectus hesperus. Protein architectures are markedly divergent between AgSF1 and AgSF2, as well as traditional spider silk fibroin family members, suggesting connection joints consist of a complex proteinaceous network. AgSF2 represents a nonglycosylated 40-kDa protein that has novel internal amino acid block repeats with the consensus sequence NVNVN embedded in a glycine-rich matrix. Analysis of the amino acid sequence of AgSF1 reveals pentameric QPGSG iterations that are similar to conserved modular elements within mammalian elastin, a rubber-like elastomeric protein that interfaces with collagen. Wet-spinning methodology using purified recombinant proteins show AgSF1 has the potential to self-assemble into fibers. X-ray fiber diffraction studies performed on these synthetic fibers reveal the presence of noncrystalline domains that resemble classical rubber networks. Collectively, these data support that the aggregate gland serves to extrude a protein mixture that contains substances that allow for the self-assembly of fiber-like structures that interface with dragline silks to mediate prey capture.
authors.affiliation: Department of Biological Sciences, University of the Pacific, Stockton, California 95211, USA.
authors.forename: Keshav
authors.initials: K
authors.lastname: Vasanthavada
authors.forename: Xiaoyi
authors.initials: X
authors.lastname: Hu
authors.forename: Tiffany
authors.initials: T
authors.lastname: Tuton-Blasingame
authors.forename: Yang
authors.initials: Y
authors.lastname: Hsia
authors.forename: Sujatha
authors.initials: S
authors.lastname: Sampath
authors.forename: Ryan
authors.initials: R
authors.lastname: Pacheco
authors.forename: Jordan
authors.initials: J
authors.lastname: Freeark
authors.forename: Arnold M
authors.initials: AM
authors.lastname: Falick
authors.forename: Simon
authors.initials: S
authors.lastname: Tang
authors.forename: Justine
authors.initials: J
authors.lastname: Fong
authors.forename: Kristin
authors.initials: K
authors.lastname: Kohler
authors.forename: Coby
authors.initials: C
authors.lastname: La Mattina-Hawkins
authors.forename: Craig
authors.initials: C
authors.lastname: Vierra
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001740:Black Widow Spider / Q000737:chemistry* / Q000235:genetics; D005349:Fibroins / Q000737:chemistry* / Q000235:genetics; D008969:Molecular Sequence Data; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary
chemical_list: D005349:Fibroins