Unique Material Properties of Bombyx mori Silk Fiber Incorporated with 3-Azidotyrosine

Residue-Specific Incorporation of Noncanonical Amino Acids in Auxotrophic Hosts: Quo Vadis?

The residue-specific incorporation of noncanonical amino acids in auxotrophic hosts allows the global exchange of a canonical amino acid with its noncanonical analog. Noncanonical amino acids are not encoded by the standard genetic code, but they carry unique side chain chemistries, e.g., to perform bioorthogonal conjugation reactions or to manipulate the physicochemical properties of a protein such as folding and stability. The method was introduced nearly 70 years ago and is still in widespread use because of its simplicity and robustness. In our study, we review the trends in the field during the last two decades. We give an overview of the application of the method for artificial post-translational protein modifications and the selective functionalization and directed immobilization of proteins. We highlight the trends in the use of noncanonical amino acids for the analysis of nascent proteomes and the engineering of enzymes and biomaterials, and the progress in the biosynthesis of amino acid analogs. We also discuss the challenges for the scale-up of the technique.

Engineering of Silkworm Tyrosyl-tRNA Synthetase Variants to Create Halogenated Silk Fiber with Improved Thermal Stability

Silk fiber, produced by the silkworm Bombyx mori, is a protein fiber with an excellent mechanical strength and broad biocompatibility. Multiple approaches, including genetic and chemical methods, must be combined to tailor silk fiber properties for wide applications, such as textiles and biomaterials. Genetic code expansion (GCE) is an alternative method to alter proteins' chemical and physical properties by incorporating synthetic amino acids into their primary structures. Here, we report an efficient system for selecting variants of B. mori tyrosyl-tRNA synthetase (BmTyrRS) used for GCE in silkworms. Four BmTyrRS variants with expanded substrate recognition toward halogenated tyrosine (Tyr) derivatives were selected, and transgenic silkworms expressing these variants were generated. The silkworms incorporated halogenated Tyr derivatives into silk fibroin to produce halogenated silk fiber with improved thermal stability. These results demonstrate the power of GCE to create protein materials with improved physical properties.

LEF3 phosphorylation attenuates the replication of Bombyx mori nucleopolyhedrovirus by suppressing its interaction with alkaline nuclease

Late expression factor 3 (LEF3), a multifunctional single-stranded DNA binding protein encoded by baculoviruses, is indispensable for viral DNA replication and plays a pivotal role in viral infection. Our previous quantitative analysis of phosphorylomics revealed that the phosphorylation levels of two serine residues (S8 and S25) located in LEF3 nuclear localization sequence were significantly up-regulated after Bombyx mori nucleopolyhedrovirus (BmNPV) infection, but the underlying mechanism remained unknown. To investigate the impact of phosphorylation on BmNPV infection, site-direct mutagenesis was performed on LEF3 to obtain phosphorylated mimic (S/D) or dephosphorylated mimic (S/A) mutants. The results demonstrated that the viral replication and proliferation were inhibited by phosphorylation of S8 or S25. Furthermore, we found that the N-terminal 125 amino acids region was responsible for interacting with virus-encoded alkaline nuclease, but this interaction could be suppressed by the phosphorylation. Our findings indicated that phosphorylation may serve as an antiviral strategy for host.

Genetic Code Expansion of the Silkworm Bombyx mori Using a Pyrrolysyl-tRNA Synthetase/tRNAPyl Pair

The domesticated silkworm Bombyx mori, an essential industrial animal for silk production, has attracted attention as a host for protein production due to its remarkable protein synthesis capability. Here, we applied genetic code expansion (GCE) using a versatile pyrrolysyl-tRNA synthetase (PylRS)/tRNAPyl pair from Methanosarcina mazei to B. mori; GCE enables synthetic amino acid incorporation into proteins to give them non-natural functions. Transgenic B. mori lines expressing M. mazei PylRS and its cognate tRNAPyl were generated and cross-mated to obtain their F1 hybrid. Orally administering a click-compatible synthetic amino acid, trans-cyclooctene-lysine (TCO-Lys), to the F1 hybrid has led to the production of silk fiber incorporated with TCO-Lys. TCO-Lys incorporation in silk fiber was verified by selective labeling of the TCO group by click chemistry. The developed system is available for large-scale protein production with a wide variety of synthetic amino acids.

Noncanonical Amino Acid Incorporation in Animals and Animal Cells

Noncanonical amino acids (ncAAs) are synthetic building blocks that, when incorporated into proteins, confer novel functions and enable precise control over biological processes. These small yet powerful tools offer unprecedented opportunities to investigate and manipulate various complex life forms. In particular, ncAA incorporation technology has garnered significant attention in the study of animals and their constituent cells, which serve as invaluable model organisms for gaining insights into human physiology, genetics, and diseases. This review will provide a comprehensive discussion on the applications of ncAA incorporation technology in animals and animal cells, covering past achievements, current developments, and future perspectives.

Egg Cooling After Oviposition Extends the Permissive Period for Microinjection-Mediated Genome Modification in Bombyx mori

In general, transgenesis efficiency is largely dependent on the developmental status of eggs for microinjection. We investigated whether the relationship between transgenesis efficiency and cooling eggs in silkworms, Bombyx mori, affects the transgenesis frequencies. First, we performed a microinjection using eggs of different developmental statuses at 25 °C. As a result, the use of eggs at 4 h after egg-laying (hAEL) demonstrated nearly five times greater efficiency in frequency compared to 8 hAEL but no transgenesis was found at 12 hAEL. Second, we examined the use of eggs stored for 5 or 24 h at 10 °C. We found that transgenic silkworms were produced not only 5 hAEL but also 24 hAEL. Finally, in the BmBLOS2 gene knock-out experiment, eggs stored at 10 °C demonstrated knock-out phenotypes even 48 hAEL at the time of injection (G0). These results demonstrate that an egg cooling treatment enables drastically enhanced rates of efficiency for insect genome modification. Our results could be useful in other insects, especially species with an extremely short syncytial preblastodermal stage.

Expanding the Genetic Code of Bioelectrocatalysis and Biomaterials

Genetic code expansion is a promising genetic engineering technology that incorporates noncanonical amino acids into proteins alongside the natural set of 20 amino acids. This enables the precise encoding of non-natural chemical groups in proteins. This review focuses on the applications of genetic code expansion in bioelectrocatalysis and biomaterials. In bioelectrocatalysis, this technique enhances the efficiency and selectivity of bioelectrocatalysts for use in sensors, biofuel cells, and enzymatic electrodes. In biomaterials, incorporating non-natural chemical groups into protein-based polymers facilitates the modification, fine-tuning, or the engineering of new biomaterial properties. The review provides an overview of relevant technologies, discusses applications, and highlights achievements, challenges, and prospects in these fields.

Proteins for Applied and Functional Materials

Shifting from a petroleum-based plastic society to a newer one built on circular economy principles requires maximizing the use of renewable resources and resolving the challenges that come with their use. Biopolymers have taken an important role in the design of biobased materials with functional properties, especially those derived from biomass available at a large scale. A number of recent studies have shown how proteins have a new dimension in developing functional materials, taking a step forward from their traditional use in food and biomedicine. Correlating the amino acidic profile of proteins at the nanoscale with their thermomechanical properties at the macroscale enables us to translate these precision polymers into a versatile design of materials, targeting large-scale applications such as foams and food packaging. Moreover, the advances in understanding proteins from a bottom-up perspective reached promising achievements for their use in applications that were not foreseen before, including biosensors, optoelectronics, and semiconductors.

Study on the Structure and Properties of Silk Fibers Obtained from Factory All-Age Artificial Diets

The traditional production mode of the sericulture industry is no longer suitable for the development requirements of modern agriculture; to facilitate the sustainable development of the sericulture industry, factory all-age artificial diet feeding came into being. Understanding the structural characteristics and properties of silk fibers obtained from factory all-age artificial diet feeding is an important prerequisite for application in the fields of textiles, clothing, biomedicine, and others. However, there have been no reports so far. In this paper, by feeding silkworms with factory all-age artificial diets (AD group) and mulberry leaves (ML group), silk fibers were obtained via two different feeding methods. The structure, mechanical properties, hygroscopic properties, and degradation properties were studied by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Structurally, no new functional groups appeared in the AD group. Compared with the ML group, the structure of the two groups was similar, and there was no significant difference in mechanical properties and moisture absorption. The structure of degummed silk fibers is dominated by crystalline regions, but α-chymotrypsin hydrolyzes the amorphous regions of silk proteins, so that after 28 d of degradation, the weight loss of both is very small. This provides further justification for the feasibility of factory all-age artificial diets for silkworms.