Expression of BmSPI38 tandem multimers in Escherichia coli and its antifungal activity / 生物工程学报

The aim of this study was to prepare tandem multimeric proteins of BmSPI38, a silkworm protease inhibitor, with better structural homogeneity, higher activity and stronger antifungal ability by protein engineering. The tandem multimeric proteins of BmSPI38 were prepared by prokaryotic expression technology. The effects of tandem multimerization on the structural homogeneity, inhibitory activity and antifungal ability of BmSPI38 were explored by in-gel activity staining of protease inhibitor, protease inhibition assays and fungal growth inhibition experiments. Activity staining showed that the tandem expression based on the peptide flexible linker greatly improved the structural homogeneity of BmSPI38 protein. Protease inhibition experiments showed that the tandem trimerization and tetramerization based on the linker improved the inhibitory ability of BmSPI38 to microbial proteases. Conidial germination assays showed that His6-SPI38L-tetramer had stronger inhibition on conidial germination of Beauveria bassiana than that of His6-SPI38-monomer. Fungal growth inhibition assay showed that the inhibitory ability of BmSPI38 against Saccharomyces cerevisiae and Candida albicans could be enhanced by tandem multimerization. The present study successfully achieved the heterologous active expression of the silkworm protease inhibitor BmSPI38 in Escherichia coli, and confirmed that the structural homogeneity and antifungal ability of BmSPI38 could be enhanced by tandem multimerization. This study provides important theoretical basis and new strategies for cultivating antifungal transgenic silkworm. Moreover, it may promote the exogenous production of BmSPI38 and its application in the medical field.

Investigating effect of Faeces Bombycis on intestinal microflora in rats with syndrome of damp retention in middle-jiao by high-throughput sequencing / 中国中药杂志

The aim of this paper was to investigate the effect of Faeces Bombycis(FB) on the intestinal microflora in rats with syndrome of damp retention in middle-jiao, and to explore its mechanism in regulating intestinal microflora from the perspective of microorganisms contained in FB. The contents of antidiuretic hormone(ADH) and C-reactive protein(CRP) in serum and aquaporin 3(AQP3) in jejunum were determined by enzyme-linked immunosorbent assay(ELISA). Illumina Miseq platform was used for high-throughput sequencing of the rat feces and FB. The ELISA results showed that as compared with the normal control group, the contents of ADH and CRP in the model group were significantly increased(P<0.05), and the content of AQP3 was significantly decreased(P<0.05). After drug administration, the ADH, CRP and AQP3 contents were recovered. Sequencing of rat feces showed that the ACE, Chao1 and Shannon indexes of the intestinal microflora were the lowest in the model group. As compared with the normal control group, the levels from phylum to genus were all significantly changed in model group, and Proteobacteria, Acinetobacter, Anaerobacter, Pseudomonas, and Parabacteroides levels were significantly increased(P<0.05), while Marvinbryantia level was significantly decreased(P<0.05). As compared with the model group, Proteobacteria was significantly decreased in the FB low and high dose groups(P<0.05), and Acinetobacter, Anaerobacter, Pseudomonas, Parabacteroides levels were significantly decreased in the low, medium and high dose groups(P<0.05), while Lachnoanaerobaculum, Intestinimonas and Marvinbryantia were increased significantly in the high dose group(P<0.05). Sequencing analysis of FB showed that the relative abundance of Leclercia, Pantoea, Brachybacterium, Shimwellia, Hartmannibacter, Klebsiella, Serratia, Aurantimonas, Paenibacillus and Bacillus was high in the FB, but they were basically not present or little in the rat feces. In conclusion, FB may play a role in the treatment of "syndrome of damp retention in middle-jiao" by balancing the intestinal microflora, and this effect may be related to the metabolites of microorganisms in the FB.

Allergenic Characterization of 27-kDa Glycoprotein, a Novel Heat Stable Allergen, from the Pupa of Silkworm, Bombyx mori

Boiled silkworm pupa is a traditional food in Asia, and patients with silkworm pupa food allergy are common in these regions. Still now only one allergen from silkworm, arginine kinase, has been identified. The purpose of this study was to identify novel food allergens in silkworm pupa by analyzing a protein extract after heat treatment. Heat treated extracts were examined by proteomic analysis. A 27-kDa glycoprotein was identified, expressed in Escherichia coli, and purified. IgE reactivity of the recombinant protein was investigated by ELISA. High molecular weight proteins (above 100 kDa) elicited increased IgE binding after heat treatment compared to that before heat treatment. The molecular identities of these proteins, however, could not be determined. IgE reactivity toward a 27-kDa glycoprotein was also increased after heating the protein extract. The recombinant protein was recognized by IgE antibodies from allergic subjects (33.3%). Glycation or aggregation of protein by heating may create new IgE binding epitopes. Heat stable allergens are shown to be important in silkworm allergy. Sensitization to the 27-kDa glycoprotein from silkworm may contribute to elevation of IgE to silkworm.

Resistance to Toxoplasma gondii Infection in Mice Treated with Silk Protein by Enhanced Immune Responses

This study investigated whether elevated host immune capacity can inhibit T. gondii infection. For this purpose, we used silk protein extracted from Bombyx mori cocoons as a natural supplement to augment immune capacity. After silk protein administration to BALB/c mice for 6 weeks, ratios of T lymphocytes (CD4+ and CD8+ T-cells) and splenocyte proliferative capacities in response to Con A or T. gondii lysate antigen (TLA) were increased. Of various cytokines, which regulate immune systems, Th1 cytokines, such as IFN-gamma, IL-2, and IL-12, were obviously increased in splenocyte primary cell cultures. Furthermore, the survival of T. gondii (RH strain)-infected mice increased from 2 days to 5 or more days. In a state of immunosuppression induced by methylprednisolone acetate, silk protein-administered mice were resistant to reduction in T-lymphocyte (CD4+ and CD8+ T-cells) numbers and the splenocyte proliferative capacity induced by Con A or TLA with a statistical significance. Taken together, our results suggest that silk protein augments immune capacity in mice and the increased cellular immunity by silk protein administration increases host protection against acute T. gondii infection.

Crystal structure of raw pure Mysore silk fibre based on (Ala-Gly)2-Ser-Gly peptide sequence using Linked-Atom-Least-Squares method.

We have carried out crystal structure analysis of raw pure Mysore silk fibers belonging to Bombyx mori on the basis of model parameters of Marsh et al using Linked-Atom-Least-Squares technique. The intensity of all the reflections were computed employing CCP13 software. We observe that the molecular modification is essentially same as b-pleated structure with antipolar-antiparallel arrangements formed by hydrogen bonds. The essential differences observed in the structure are highlighted and discussed.