Amino acid composition of spider silks
TL;DR: The amino acid composition is reported for the secretions present in the various silk glands in the female garden spider, Araneus diadematus, and it is shown that the large and the small ampullate glands produce different types of secretion.
About: This article is published in Comparative Biochemistry and Physiology.The article was published on 1970-08-01. It has received 165 citations till now. The article focuses on the topics: Araneus diadematus.
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TL;DR: Successful copying of the spider's internal processing and precise control over protein folding, combined with knowledge of the gene sequences of its spinning dopes, could permit industrial production of silk-based fibres with unique properties under benign conditions.
Abstract: Spider silk has outstanding mechanical properties despite being spun at close to ambient temperatures and pressures using water as the solvent. The spider achieves this feat of benign fibre processing by judiciously controlling the folding and crystallization of the main protein constituents, and by adding auxiliary compounds, to create a composite material of defined hierarchical structure. Because the 'spinning dope' (the material from which silk is spun) is liquid crystalline, spiders can draw it during extrusion into a hardened fibre using minimal forces. This process involves an unusual internal drawdown within the spider's spinneret that is not seen in industrial fibre processing, followed by a conventional external drawdown after the dope has left the spinneret. Successful copying of the spider's internal processing and precise control over protein folding, combined with knowledge of the gene sequences of its spinning dopes, could permit industrial production of silk-based fibres with unique properties under benign conditions.
1,433 citations
Cites background from "Amino acid composition of spider si..."
...Composition of a thread Spider and insect silks have the same basic building blocks: proteins made largely from non-essential amino acid...
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TL;DR: Comparison of MA silks from Araneus diadematus and Nephila clavipes shows variation in fibroin sequence and properties between spider species provides the opportunity to investigate the design of these remarkable biomaterials.
Abstract: Spiders produce a variety of silks, and the cloning of genes for silk fibroins reveals a clear link between protein sequence and structure-property relationships. The fibroins produced in the spider's major ampullate (MA) gland, which forms the dragline and web frame, contain multiple repeats of motifs that include an 8-10 residue long poly-alanine block and a 24-35 residue long glycine-rich block. When fibroins are spun into fibres, the poly-alanine blocks form (b)-sheet crystals that crosslink the fibroins into a polymer network with great stiffness, strength and toughness. As illustrated by a comparison of MA silks from Araneus diadematus and Nephila clavipes, variation in fibroin sequence and properties between spider species provides the opportunity to investigate the design of these remarkable biomaterials.
1,037 citations
Cites background from "Amino acid composition of spider si..."
...Molecular genetics of the spider fibroin gene family Until recently, we knew little about the amino acid sequence motifs in spider fibroins, although we knew that each of the seven glands produced proteins with unique amino acid compositions (Andersen, 1970)....
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...Until recently, we knew little about the amino acid sequence motifs in spider fibroins, although we knew that each of the seven glands produced proteins with unique amino acid compositions (Andersen, 1970)....
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TL;DR: An acid-soluble protein was extracted and purified from the phenol gland located in the byssus-secreting foot of the fouling marine mussel, and its composition and its sticky tendencies in vitro strongly suggest that it contributes to byssal adhesion.
Abstract: The fouling marine mussel Mytilus edulis attaches itself to various substrates by spinning byssal threads, the adhesive discs of which are rich in the amino acid 3,4-dihydroxyphenylalanine (dopa). An acid-soluble protein was extracted and purified from the phenol gland located in the byssus-secreting foot of the animal. This protein is highly basic and contains large amounts of lysine, dopa, and 3- and 4-hydroxyproline. The composition of this protein and its sticky tendencies in vitro strongly suggest that it contributes to byssal adhesion.
912 citations
TL;DR: In this article, the structure and properties of silks are matched to their mechanical function to increase the general understanding of structure-property relationships in fibrous polymers, and the results showed that these properties can be used to improve the structural properties of polymers.
580 citations
TL;DR: In this article, the structure and function of silk proteins produced naturally by silkworms and spiders are discussed, followed by the biological and technical processing of Silk proteins into a variety of morphologies (including capsules, fibers, films, foams, gels and spheres).
489 citations
References
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TL;DR: In this article, it was shown that probably all the fibroins are made up of anti-parallel pleated sheets of polypeptide chains, the difference between the fibres produced by the silk-spinning organisms belonging to the orders Lepidoptera and Araneae has been attributed to the variation in, and sequence of, the amino acid residues composing the polyprotein chains.
247 citations
TL;DR: By using intensities of absorption at 2944and 280 m,, determined by means of a photoelectric spectrophotometer, mixtures of tyrosine and tryptophan may be analyzed with considerable accuracy provided the molar ratios are not greater than 20:1 either way.
Abstract: 1. The ultra-violet absorption spectra of tyrosine and tryptophan have been determined in 0 1 NNaOH and the curves found to intersect at 257*15 and 294-4 m,u (E, 2748 and 2375, respectively). 2. By using intensities of absorption at 2944and 280 m,, determined by means of a photoelectric spectrophotometer, mixtures of tyrosine and tryptophan may be analyzed with considerable accuracy provided the molar ratios are not greater than 20:1 either way. 3. Using about 25 mg. of material, proteins may be analyzed with comparable accuracy if due correction is made for irrelevant continuous absorption.
229 citations
TL;DR: The amino acid composition of 74 fibroins from various silk-producing arthropods has been determined, 26 of them being analysed quantitatively, and the remainder semi-quantitatively after paper chromatography as mentioned in this paper.
141 citations
TL;DR: A striking correlation between proline content and extent of helical configuration is demonstrated and it is suggested that proline interferes with the formation of the a-helix configuration.
Abstract: Optical rotation can be used to detect the presence of helical configurations of the polypeptide chains in proteins, to determine screw sense, and to estimate the extent of helical regions ( 1 ) . Moffitt's theory ( l a ) of rotatory dispersion for helical macromolecules has been successfully applied to synthetic polypeptides ( 2 ) and to proteins (2, 3 ) , and at the present time it may be applied empirically to estimate a-helix content. Globular proteins have been shown to have relatively low ( 2 ) and fibrous proteins to have relatively high ( 3 ) helix content. We have examined the amino acid composition of proteins which belong to the keratin-myosin-epidermin-fibrinogen class (KMEF proteins) to account for the wide variation in amount of a-helix present; in this report we demonstrate a striking correlation between proline content and extent of helical configuration. Table 1 lists data obtained by proline determinations using the method of Troll and Lindsley ( 4 ) . Helix content is based on rotatory dispersion measurcmcnts reported previously ( 3 ) . Wc assume for this discussion that light mcromyosin fraction I is 100-percent helical and that the helices have a single sense of twist. Fragmentation of myosin by tryptic digestion into light meromyosin and heavy meromyosin corresponds to a fractionation into one component relatively poor and one relatively rich in proline. Furthermore, the light meromyosin may be separated by ethanol into two fractions differing in prolinc content, one of which (light meromyosin fraction I ) remains soluble after treatment with ethanol concentrations of 50 percent (volume by volume) or higher and represents about 25 percent of the intact myosin by weight ( 5 ) . In each case, the higher the a-helix content, the lower the amount of proline present. These results suggest that proline interferes ~v i th the formation of the a-helical configuration. By adopting a very simple model for the a-proteins consisting of helical and nonhelical regions, one may estimate the disordering effect of a single proline residue, assuming that the proline is distributed statistically. Table 1 shows that, on the average, each proline residue is associated with 15 to 20 residues (hence several helical turns) not participating in the right-handed a-helical configuration in aqueous solution. In nonaqueous solution, this effect may be decreased ( 2 ) . These obsenlations are supported by model building from which it is seen that the pyrrolidines do not fit well into a right-handed a-helix. Available data on proteins other than the KMEF series show a generally similar correlation of proline and helix content. On the basis of dispersion studies (2, 3 ) , onc may take the specific rotation of n ~ t i v e proteins in aqueous solution as inversely proportional to the a-helix content. Thus, a fully-coiled right-handed a-helix may be characteri7ed by [a',, r O 0 ( 2 ) and nonhelical chains by ;a], LZ 100' 16). Globular proteins have rotations [a:, r30' to 60°, correspondin? to low helix content of about 30 to 40 percent ( 2 ) . Tristram's compilations ( 7 ) show that these proteins contain from 3 to 8 percent proline, corresponding to values expected from the data given above on the KMEF series. Exceptions such as lysozyme, insulin, and avidin having less than 2 percent proline might be accounted f o r by sulfur or phosphorus cross-linka~es which may interfere with a-helix formation. I t should be noted that such cross-linkages, as well as sidechain interactions, may stabili~e or disrupt helical confiqurations (8 ) . Thus the KhfEF proteins discussed above, having few if any sulfur cross-linkages (fibrinown cxccpted), provide simpler systems for thiq correlation than do thc \"globular\" proteins ( 9 ) . Proline content higher than about 8 percent would be expected to cause almost completc absence of thc a-helix, provided that the prolinc residues do not exiit as \"blocks\" in the polvpeptide chain. The rotation of casein [a], r 100' 11'1) sunporti: thii idca, and rotatory dispersion data on casein and the prolamines chould bc of considerable interest ( 11\\ . Collagen has an exceptionall) high pyrrolidine content (about 25-percent), but rather than assuming a nonhelical configuration, the polypeptide chains in collagen comprise a cable of three left-handed helices, each similar Table 1. Helix content and proline concentration of KMEF proteins.
105 citations
52 citations