Fifty years later: The sequence, structure and function of lacewing cross-beta silk

Weisman, Sarah; Okada, Shoko; Mudie, Stephen; Huson, Mickey G.; Trueman, Holly E.; Sriskantha, Alagacone; Haritos, Victoria S.; Sutherland, Tara D.

doi:10.1016/j.jsb.2009.07.002

Cited by 39 publications

(70 citation statements)

References 18 publications

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“…106 In the case of functional amyloid, the ability to exploit an environmental niche has resulted in retention of these sequences. 16,107,108 These earlier conclusions are borne out by this study, which shows that in native proteins there is a greater tendency for amyloidogenic sequences to form either a helical or b strand secondary structure rather than random coil. Furthermore, the results show that potentially fibril-forming residues in bstrand conformation are more buried than non-fibrilforming residues.…”

Section: Discussionsupporting

confidence: 58%

Amyloidogenic sequences in native protein structures

Tzotzos

Doig

2010

Protein Science

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Numerous short peptides have been shown to form b-sheet amyloid aggregates in vitro.Proteins that contain such sequences are likely to be problematic for a cell, due to their potential to aggregate into toxic structures. We investigated the structures of 30 proteins containing 45 sequences known to form amyloid, to see how the proteins cope with the presence of these potentially toxic sequences, studying secondary structure, hydrogen-bonding, solvent accessible surface area and hydrophobicity. We identified two mechanisms by which proteins avoid aggregation: Firstly, amyloidogenic sequences are often found within helices, despite their inherent preference to form b structure. Helices may offer a selective advantage, since in order to form amyloid the sequence will presumably have to first unfold and then refold into a b structure. Secondly, amyloidogenic sequences that are found in b structure are usually buried within the protein. Surface exposed amyloidogenic sequences are not tolerated in strands, presumably because they lead to protein aggregation via assembly of the amyloidogenic regions. The use of a-helices, where amyloidogenic sequences are forced into helix, despite their intrinsic preference for b structure, is thus a widespread mechanism to avoid protein aggregation.

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Section: Discussionsupporting

confidence: 58%

Amyloidogenic sequences in native protein structures

Tzotzos

Doig

2010

Protein Science

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“…In contrast, the only protein structure reported to exist in glow-worm silk are cross-β-sheets, in which the β-strands are arranged perpendicular to the fibre axis (Rudall, 1962). Cross-β-sheet crystallites also occur in silks made by insects that have evolved silk production independently to either glow-worms or spiders, such as lacewings (order Neuroptera; Weisman et al, 2009), hyperine weevils (Coleoptera: Curculionidae; Kenchington, 1983) and water scavenger beetles (Coleoptera: Hydrophilidae; Rudall, 1962). Interestingly, it is known that cross-β-sheet crystallites are able to confer extensibility to silk fibres due to the ability of the crystallites to unravel under tension and form extended-β-sheet structures, a process that is strictly dependent on the presence of water acting as a hydrogen bond donor and plasticiser (Bauer et al, 2012;Kenchington, 1983;Rudall, 1962;Weisman et al, 2009).…”

Section: Accepted M Manuscriptmentioning

confidence: 99%

The other prey-capture silk: Fibres made by glow-worms (Diptera: Keroplatidae) comprise cross-β-sheet crystallites in an abundant amorphous fraction

Walker

Weisman

Trueman

et al. 2015

Comparative Biochemistry and Physiology Part B: Biochemistry an

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The other prey-capture silk: Fibres made by glow-worms (Diptera: Keroplatidae) comprise cross-β-sheet crystallites in an abundant amorphous fraction, Comparative Biochemistry and Physiology, Part B (2015), doi: 10.1016/j.cbpb.2015 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Keywords: silk; Arachnocampa; glow-worm; cross-β-sheet; flagelliform; extensibility; disordered A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT AbstractGlow-worms (larvae of dipteran genus Arachnocampa) are restricted to moist habitats where they capture flying prey using snares composed of highly extensible silk fibres and sticky mucus droplets.Little is known about the composition or structure of glow-worm snares, or the extent of possible convergence between glow-worm and arachnid capture silks. We characterised Arachnocampa richardsae silk and mucus using X-ray scattering, Fourier transform infrared spectroscopy and amino acid analysis. Silk but not mucus contained crystallites of the cross-β-sheet type, which occur in unrelated insect silks but have not been reported previously in fibres used for prey capture. Mucus proteins were rich in Gly (28.5%) and existed in predominantly a random coil structure, typical of many adhesive proteins. In contrast, the silk fibres were unusually rich in charged and polar residues, particularly Lys (18.1%), which we propose is related to their use in a highly hydrated state.Comparison of X-ray scattering, infrared spectroscopy and amino acid analysis data suggests that silk fibres contain a high fraction of disordered protein. We suggest that in the native hydrated state, silk fibres are capable of extension via deformation of both disordered regions and cross-β-sheet crystallites, and that high extensibility is an adaptation promoting successful prey capture. This study illustrates the rich variety of protein motifs that are available for recruitment into biopolymers, and how convergently evolved materials can nevertheless be based on fundamentally different protein structures.

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“…solid transition. In many silks of both the canonical and non-canonical types, covalent cross-linking upon extrusion, either owing to oxidative cross-linking through cysteine residues or due to enzymatic tanning, may assist aggregation and solidification [7,25]. However, covalent cross-linking is not a requisite feature of fabrication of either canonical or non-canonical silk proteins, as demonstrated by the potential for silkworm, hornet and sawfly silks to be dissolved in chaotropic solutions without reducing agents [26][27][28].…”

Section: (I) Overcoming Flow Viscositymentioning

confidence: 99%

“…Orb-spider dragline silk is composed of two major proteins, MaSp1 and MaSp2, which have molecular weights in the range 250-500 kDa [3]. [7]. Analysis of non-canonical silk protein amino acid sequences suggests they have a common elongated tertiary structure.…”

Section: Comparison Of Canonical and Non-canonical Silk Proteins (A) mentioning

confidence: 99%

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More than one way to spin a crystallite: multiple trajectories through liquid crystallinity to solid silk

2015

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Arthropods face several key challenges in processing concentrated feedstocks of proteins (silk dope) into solid, semi-crystalline silk fibres. Strikingly, independently evolved lineages of silk-producing organisms have converged on the use of liquid crystal intermediates (mesophases) to reduce the viscosity of silk dope and assist the formation of supramolecular structure. However, the exact nature of the liquid-crystal-forming-units (mesogens) in silk dope, and the relationship between liquid crystallinity, protein structure and silk processing is yet to be fully elucidated. In this review, we focus on emerging differences in this area between the canonical silks containing extended-bsheets made by silkworms and spiders, and 'non-canonical' silks made by other insect taxa in which the final crystallites are coiled-coils, collagen helices or cross-b-sheets. We compared the amino acid sequences and processing of natural, regenerated and recombinant silk proteins, finding that canonical and non-canonical silk proteins show marked differences in length, architecture, amino acid content and protein folding. Canonical silk proteins are long, flexible in solution and amphipathic; these features allow them both to form large, micelle-like mesogens in solution, and to transition to a crystallite-containing form due to mechanical deformation near the liquidsolid transition. By contrast, non-canonical silk proteins are short and have rod or lath-like structures that are well suited to act both as mesogens and as crystallites without a major intervening phase transition. Given many non-canonical silk proteins can be produced at high yield in E. coli, and that mesophase formation is a versatile way to direct numerous kinds of supramolecular structure, further elucidation of the natural processing of non-canonical silk proteins may to lead to new developments in the production of advanced protein materials.

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Fifty years later: The sequence, structure and function of lacewing cross-beta silk

Cited by 39 publications

References 18 publications

Amyloidogenic sequences in native protein structures

Amyloidogenic sequences in native protein structures

The other prey-capture silk: Fibres made by glow-worms (Diptera: Keroplatidae) comprise cross-β-sheet crystallites in an abundant amorphous fraction

More than one way to spin a crystallite: multiple trajectories through liquid crystallinity to solid silk

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