Evidence from flagelliform silk cDNA for the structural basis of elasticity and modular nature of spider silks (original) (raw)
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Hypotheses that correlate the sequence, structure, and mechanical properties of spider silk proteins
International Journal of Biological Macromolecules, 1999
Several types of silks and silk protein coding genes have been characterized from orb-web weaving spiders. When the protein sequences of major ampullate, minor ampullate, and flagelliform silks from Nephila cla6ipes are compared, they can be summarized as sets of shared amino acid motifs. Four of these motifs and their likely secondary structures are described. Each structural element, termed a module, is then associated with its impact on the mechanical properties of a silk fiber. In particular, correlations are drawn between an alanine-rich 'crystalline module' and tensile strength and between a proline-containing 'elasticity module' and extensibility.
Protein families, natural history and biotechnological aspects of spider silk
Genetics and Molecular Research, 2012
ABSTRACT. Spiders are exceptionally diverse and abundant organisms in terrestrial ecosystems and their evolutionary success is certainly related to their capacity to produce different types of silks during their life cycle, making a specialized use on each of them. Presenting particularly tandemly arranged amino acid repeats, silk proteins (spidroins) have mechanical properties superior to most synthetic or natural high-performance fibers, which makes them very promising for biotechnology industry, with putative applications in the ...
Applied Physics A, 2006
Orb-web weavers can produce up to six different types of silk and a glue for various functions. Tubuliform silk is unique among them due to its distinct amino acid composition, specific time of production, and atypical mechanical properties. To study the protein composing this silk, tubuliform gland cDNA libraries were constructed from three orbweaving spiders Argiope aurantia, Araneus gemmoides, and Nephila clavipes. Amino acid composition comparison between the predicted tubuliform silk protein sequence (TuSp1) and the corresponding gland protein confirms that TuSp1 is the major component in tubuliform gland in three spiders. Sequence analysis suggests that TuSp1 shares no significant similarity with its paralogues, while it has conserved sequence motifs with the most primitive spider, Euagrus chisoseus silk protein. The presence of large side-chain amino acids in TuSp1 sequence is consistent with the frustrated β-sheet crystalline structure of tubuliform silk observed in transmission electron microscopy. Repeat unit comparison within species as well as among three spiders exhibits high sequence conservation. Parsimony analysis based on carboxy terminal sequence shows that Argiope and Araneus are more closely related than either is to Nephila which is consistent with phylogenetic analysis based on morphological evidence.
Molecular Biology and Evolution, 2013
Spider silk fibers have impressive mechanical properties and are primarily composed of highly repetitive structural proteins (termed spidroins) encoded by a single gene family. Most characterized spidroin genes are incompletely known because of their extreme size (typically >9 kb) and repetitiveness, limiting understanding of the evolutionary processes that gave rise to their unusual gene architectures. The only complete spidroin genes characterized thus far form the dragline in the Western black widow, Latrodectus hesperus. Here, we describe the first complete gene sequence encoding the aciniform spidroin AcSp1, the primary component of spider prey-wrapping fibers. L. hesperus AcSp1 contains a single enormous ($19 kb) exon. The AcSp1 repeat sequence is exceptionally conserved between two widow species ($94% identity) and between widows and distantly related orb-weavers ($30% identity), consistent with a history of strong purifying selection on its amino acid sequence. Furthermore, the 16 repeats (each 371-375 amino acids long) found in black widow AcSp1 are, on average, >99% identical at the nucleotide level. A combination of stabilizing selection on amino acid sequence, selection on silent sites, and intragenic recombination likely explains the extreme homogenization of AcSp1 repeats. In addition, phylogenetic analyses of spidroin paralogs support a gene duplication event occurring concomitantly with specialization of the aciniform glands and the tubuliform glands, which synthesize egg-case silk. With repeats that are dramatically different in length and amino acid composition from dragline spidroins, our L. hesperus AcSp1 expands the knowledge base for developing silk-based biomimetic technologies.
Orb-web weavers can produce up to six different types of silk and a glue for various functions. Tubuliform silk is unique among them due to its distinct amino acid composition, specific time of production, and atypical mechanical properties. To study the protein composing this silk, tubuliform gland cDNA libraries were constructed from three orbweaving spiders Argiope aurantia, Araneus gemmoides, and Nephila clavipes. Amino acid composition comparison between the predicted tubuliform silk protein sequence (TuSp1) and the corresponding gland protein confirms that TuSp1 is the major component in tubuliform gland in three spiders. Sequence analysis suggests that TuSp1 shares no significant similarity with its paralogues, while it has conserved sequence motifs with the most primitive spider, Euagrus chisoseus silk protein. The presence of large side-chain amino acids in TuSp1 sequence is consistent with the frustrated β-sheet crystalline structure of tubuliform silk observed in transmission electron microscopy. Repeat unit comparison within species as well as among three spiders exhibits high sequence conservation. Parsimony analysis based on carboxy terminal sequence shows that Argiope and Araneus are more closely related than either is to Nephila which is consistent with phylogenetic analysis based on morphological evidence.
Molecular Biology and Evolution, 2004
Araneoid spiders use specialized abdominal glands to produce up to seven different proteinbased silks/glues that have diverse physical properties. The fibroin sequences that encode aciniform fibers (wrapping silk) and the mechanical properties of these fibers have not been characterized previously. In order to gain a better understanding of the molecular radiation of spider silk fibroin genes, cDNA libraries derived from aciniform glands of the banded garden spider, Argiope trifasciata, were constructed, and unique silk transcripts were sequenced. There was evidence for a single silk fibroin gene that was expressed in the aciniform glands, and the inferred amino acid composition of the novel fibroin closely matched the amino acid contents of these glands. The inferred protein, aciniform spidroin 1 (AcSp1), is composed of highly homogenized repeats that are 200 amino acids in length. The long stretches of poly-alanine and glycine-alanine subrepeats, that are thought to account for the crystalline regions of minor ampullate and major ampullate fibers, are very poorly represented in AcSp1. The AcSp1 repeat unit is iterated minimally fourteen times and does not display substantial sequence similarity to any previously described genes or proteins. Database searches, however, showed that the non-repetitive carboxy-terminus contains stretches of matches to known spider fibroin sequences, suggesting that the AcSp1 gene is a highly divergent member of the spider silk gene family. In phylogenetic analyses of carboxy-terminal sequences from araneid spiders, the aciniform sequence did not group strongly with clusters of fibroins from the flagelliform, minor ampullate, or major ampullate silk glands. Comparisons of stress/strain curves for major ampullate, minor ampullate, and aciniform silks from Argiope trifasciata showed significant differences in ultimate strength, extensibility, and toughness. Remarkably, the toughness of aciniform silk was 50% greater than the highest values typically recorded for major ampullate silk. These differences in performance, in combination with the radical divergence at the sequence level among fibroin paralogues, suggest a possible linkage between silk fibroin sequences and performance that should be explored in future structural/functional studies of aciniform silk.
Diversity of Molecular Transformations Involved in the Formation of Spider Silks
Journal of Molecular Biology, 2011
Spiders that spin orb webs secrete seven types of silk. Although the spinning process of the dragline thread is beginning to be understood, the molecular events that occur in spiders' opisthosomal glands, which produce the other fibers, are unknown due to a lack of data regarding their initial and final structures. Taking advantage of the efficiency of Raman spectromicroscopy in investigating micrometer-sized biological samples, we have determined the secondary structure of proteins in the complete set of glands of the orb-weaving spider Nephila clavipes. The major and minor ampullate silks in the sac of their glands have identical secondary structures typical of natively unfolded proteins. Spidroins are converted into fibers containing highly oriented β-sheets. The capture spiral represents a distinct structural singleton. The proteins are highly disordered prior to spinning and undergo no molecular change or alignment upon spinning. The cylindrical, aciniform, and piriform proteins are folded in their initial state with a predominance of α-helices, but whereas the cylindrical gland forms a fiber similar to the major ampullate thread, the aciniform and piriform glands produce fibers dominated by moderately oriented β-sheets and α-helices. The conformation of the proteins before spinning is related to intrinsic characteristics of their primary structure. Proteins that are unfolded in the gland have repeat sequences composed of submotifs and display no sequence regions with aggregation propensity. By contrast, the folded proteins have neither submotifs nor aggregation-prone sequence regions. Taken together, the Raman data show a remarkable diversity of molecular transformations occurring upon spinning.
FUNPEC-RP www Protein families, natural history and biotechnological aspects of spider silk
Spiders are exceptionally diverse and abundant organisms in terrestrial ecosystems and their evolutionary success is certainly related to their capacity to produce different types of silks during their life cycle, making a specialized use on each of them. Presenting particularly tandemly arranged amino acid repeats, silk proteins (spidroins) have mechanical properties superior to most synthetic or natural high-performance fibers, which makes them very promising for biotechnology industry, with putative applications in the production of new biomaterials. During the evolution of spider species, complex behaviors of web production and usage have been coupled with anatomical specialization of spinning glands. Spiders retaining ancestral characters, such as the ones belonging to the Mygalomorph group, present simpler sorts of webs used mainly to build burrows and egg sacs, and their silks are produced by globular undifferentiated spinning glands. In contrast, Araneomorphae spiders have a complex spinning apparatus, presenting up to seven morphologically distinct glands, capable to Review ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 11 (3): 2360-2380 (2012)
Review Protein families, natural history and biotechnological aspects of spider silk
Genetics and Molecular Research, 2012
Spiders are exceptionally diverse and abundant organisms in terrestrial ecosystems and their evolutionary success is certainly related to their capacity to produce different types of silks during their life cycle, making a specialized use on each of them. Presenting particularly tandemly arranged amino acid repeats, silk proteins (spidroins) have mechanical properties superior to most synthetic or natural high-performance fibers, which makes them very promising for biotechnology industry, with putative applications in the production of new biomaterials. During the evolution of spider species, complex behaviors of web production and usage have been coupled with anatomical specialization of spinning glands. Spiders retaining ancestral characters, such as the ones belonging to the Mygalomorph group, present simpler sorts of webs used mainly to build burrows and egg sacs, and their silks are produced by globular undifferentiated spinning glands. In contrast, Araneomorphae spiders have a complex spinning apparatus, presenting up to seven morphologically distinct glands, capable to Review ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 11 (3): 2360-2380 (2012) Protein family, history and biotechnology of spider silk produce a more complex set of silk polymers with different degrees of rigidness and elasticity associated with distinct behaviors. Aiming to provide a discussion involving a number of spider silks' biological aspects, in this review we present descriptions of members from each family of spidroin identified from five spider species of the Brazilian biodiversity, and an evolutionary study of them in correlation with the anatomical specialization of glands and spider's spinning behaviors. Due to the biotechnological importance of spider silks for the production of new biomaterials, we also discuss about the new possible technical and biomedical applications of spider silks and the current status of it.