title: Conserved C-terminal domain of spider tubuliform spidroin 1 contributes to extensibility in synthetic fibers.
abstract: Spider silk is renowned for its extraordinary mechanical properties, having a balance of high tensile strength and extensibility. To date, the majority of studies have focused on the production of dragline silks from synthetic spider silk gene products. Here we report the first mechanical analysis of synthetic egg case silk fibers spun from the  Latrodectus hesperus  tubuliform silk proteins, TuSp1 and ECP-2. We provide evidence that recombinant ECP-2 proteins can be spun into fibers that display mechanical properties similar to other synthetic spider silks. We also demonstrate that silks spun from recombinant thioredoxin-TuSp1 fusion proteins that contain the conserved C-terminal domain exhibit increased extensibility and toughness when compared to the identical fibers spun from fusion proteins lacking the C-terminus. Mechanical analyses reveal that the properties of synthetic tubuliform silks can be modulated by altering the postspin draw ratios of the fibers. Fibers subject to increased draw ratios showed elevated tensile strength and decreased extensibility but maintained constant toughness. Wide-angle X-ray diffraction studies indicate that postdrawn fibers containing the C-terminal domain of TuSp1 have more amorphous content when compared to fibers lacking the C-terminus. Taken together, these studies demonstrate that recombinant tubuliform spidroins that contain the conserved C-terminal domain with embedded protein tags can be effectively spun into fibers, resulting in similar tensile strength but increased extensibility relative to nontagged recombinant dragline silk proteins spun from equivalently sized proteins.
authors.affiliation: Department of Biological Sciences, University of the Pacific, Stockton, California 95211, United States.
authors.forename: Eric
authors.initials: E
authors.lastname: Gnesa
authors.forename: Yang
authors.initials: Y
authors.lastname: Hsia
authors.forename: Jeffery L
authors.initials: JL
authors.lastname: Yarger
authors.forename: Warner
authors.initials: W
authors.lastname: Weber
authors.forename: Joan
authors.initials: J
authors.lastname: Lin-Cereghino
authors.forename: Geoff
authors.initials: G
authors.lastname: Lin-Cereghino
authors.forename: Simon
authors.initials: S
authors.lastname: Tang
authors.forename: Kimiko
authors.initials: K
authors.lastname: Agari
authors.forename: Craig
authors.initials: C
authors.lastname: Vierra
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D017124:Conserved Sequence; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D004548:Elasticity; D004926:Escherichia coli; D005349:Fibroins / Q000737:chemistry* / Q000235:genetics; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure; D017386:Sequence Homology, Amino Acid; D047011:Silk / Q000096:biosynthesis* / Q000648:ultrastructure; D013112:Spiders; D013718:Tensile Strength; D014961:X-Ray Diffraction
chemical_list: D018076:DNA, Complementary; D011993:Recombinant Fusion Proteins; D047011:Silk; C086087:spidroin 1; D005349:Fibroins