Critical role of minor eggcase silk component in promoting spidroin chain alignment and strong fiber formation

Natural spider silk with extraordinary mechanical properties is typically spun from more than one type of spidroin. Although the main components of various spider silks have been widely studied, little is known about the molecular role of the minor silk components in spidroin self-assembly and fiber formation. Here, we show that the minor component of spider eggcase silk, TuSp2, not only accelerates self-assembly but remarkably promotes molecular chain alignment of spidroins upon physical shearing. NMR structure of the repetitive domain of TuSp2 reveals that its dimeric structure with unique charged surface serves as a platform to recruit different domains of the main eggcase component TuSp1. Artificial fiber spun from the complex between TuSp1 and TuSp2 minispidroins exhibits considerably higher strength and Young’s modulus than its native counterpart. These results create a framework for rationally designing silk biomaterials based on distinct roles of silk components.

The balance of crystalline and amorphous regions in the fibroin structure underpins the tensile strength of bagworm silk

Protein-based materials are considered versatile biomaterials, and their biodegradability is an advantage for sustainable development. Bagworm produces strong silk for use in unique situations throughout its life stages. Rigorous molecular analyses of Eumeta variegata suggested that the particular mechanical properties of its silk are due to the coexistence of poly-A and GA motifs. However, little molecular information on closely related species is available, and it is not understood how these properties were acquired evolutionarily or whether the motif combination is a conserved trait in other bagworms. Here, we performed a transcriptome analysis of two other bagworm species (Canephora pungelerii and Bambalina sp.) belonging to the family Psychidae to elucidate the relationship between the fibroin gene and silk properties. The obtained transcriptome assemblies and tensile tests indicated that the motif combination and silk properties were conserved among the bagworms. Furthermore, our analysis showed that C. pungelerii produces extraordinarily strong silk (breaking strength of 1.4 GPa) and indicated that the cause may be the C. pungelerii -specific balance of crystalline/amorphous regions in the H-fibroin repetitive domain. This particular H-fibroin architecture may have been evolutionarily acquired to produce strong thread to maintain bag stability during the relatively long development period of Canephora species relative to other bagworms.

The wPDI Redox Cycle Coupled Conformational Change of the Repetitive Domain of the HMW-GS 1Dx5—A Computational Study

The repetitive sequence of glutenin plays an important role in dough rheology; however, its interaction with wheat protein disulfide isomerase (wPDI) remains unclear. In this study, the conformations of wild type glutenin repetitive sequence (WRS) from the high molecular weight glutenin subunit (HMW-GS) 1Dx5, an artificially designed glutenin repetitive sequence (DRS) of which the amino acid composition is the same but the primary structure is different, and wPDI under different redox states were simulated. The molecular interactions between the aforementioned repetitive sequences with wPDI under different redox states were further investigated. The results indicated that the repetitive sequences bind to the b and b′ domains of an “open”, oxidized wPDI (wPDIO) which serves as the acceptor state of substrate. The repetitive sequence is partially folded (compressed) in wPDIO, and is further folded in the thermodynamically favored, subsequent conformational transition of wPDIO to reduced wPDI (wPDIR). Compared with the artificially designed one, the naturally designed repetitive sequence is better recognized and more intensively folded by wPDI for its later unfold as the molecular basis of dough extension.

1Mx2.1, a novel high-molecular-weight glutenin subunit from Aegilops comosa and its relationship to high-quality dough

High-molecular-weight glutenin subunit (HMW-GS) of endosperm is mainly correlated with dough quality of bread wheat. In wheat cultivars, the HMW-GS genes with good processing quality are limited. However, there are an amount of excellent HMW-GS genes presenting in wheat-related species. In this work, two novel HMW-GS genes located on 1 M chromosome from Aegilops comosa have been cloned, designated as 1Mx2.1 and 1My12.1, respectively. The molecular structure of 1Mx2.1 and 1My12.1 showed high similarity with the published HMW-GS, but containing unique structures. 1Mx2.1 contained an extra cysteine residue in the repetitive domain, and 1My12.1 lost the conservative cysteine residue in the C-terminal domain. In vitro mixing test has indicated that 1Mx2.1 contributes excellent dough quality. The Ae. comosa can be used as an important genetic resource for wheat quality improvement.

Cloning and characterization of high molecular weight glutenin gene from Triticum aestivum cultivar Dacke

<p class="abstract"><strong>Background:</strong> High molecular weight (HMW) glutenin protein plays a crucial role in determining dough viscoelastic properties that determines the quality of wheat flour. The aim of the present study was to isolate, clone and analyze (<em>in silico</em>) the HMW glutenin gene of <em>Triticum aestivum</em> cultivar Dacke.</p><p class="abstract"><strong>Methods:</strong> Primers were designed to amplify a 2445 bp fragment of HMW glutenin gene. Ax type HMW glutenin gene from <em>Triticum aestivum</em> cultivar Dacke was isolated using PCR and it was sequenced by primer walking. </p><p class="abstract"><strong>Results:</strong> Amplified HMW glutenin gene was designated as HMWGAx. Sequence analysis revealed a complete open reading frame encoding 815 amino acid residues with N- and C terminal non-repetitive domain and a central repetitive domain. The calculated molecular weight of the deduced HMW glutenin protein was ~88 kDa and the number of cysteine residues in the HMWGAx was four, in accordance with other x type HMW glutenin proteins. Phylogenetic analysis revealed 100% homology to the previously studied Ax2* type HMW glutenin gene from cultivar Cheyenne. Predicted secondary structure results showed that it was similar to1Ax1 type of common wheat (<em>Triticum aestivum</em>), having superior flour milling quality.</p><p><strong>Conclusions:</strong> Sequence analysis suggests that HMWGAx protein significantly and positively correlates with the properties of elasticity and extensibility of gluten. </p>