title: Proteins in the Cocoon of Silkworm Inhibit the Growth of Beauveria bassiana.
abstract: Silk cocoons are composed of fiber proteins (fibroins) and adhesive glue proteins (sericins), which provide a physical barrier to protect the inside pupa. Moreover, other proteins were identified in the cocoon silk, many of which are immune related proteins. In this study, we extracted proteins from the silkworm cocoon by Tris-HCl buffer (pH7.5), and found that they had a strong inhibitory activity against fungal proteases and they had higher abundance in the outer cocoon layers than in the inner cocoon layers. Moreover, we found that extracted cocoon proteins can inhibit the germination of Beauveria bassiana spores. Consistent with the distribution of protease inhibitors, we found that proteins from the outer cocoon layers showed better inhibitory effects against B. bassiana spores than proteins from the inner layers. Liquid chromatography-tandem mass spectrometry was used to reveal the extracted components in the scaffold silk, the outermost cocoon layer. A total of 129 proteins were identified, 30 of which were annotated as protease inhibitors. Protease inhibitors accounted for 89.1% in abundance among extracted proteins. These protease inhibitors have many intramolecular disulfide bonds to maintain their stable structure, and remained active after being boiled. This study added a new understanding to the antimicrobial function of the cocoon.
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
authors.forename: Xiaomeng
authors.initials: X
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
authors.forename: Zhaoming
authors.initials: Z
authors.lastname: Dong
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
authors.forename: Youshan
authors.initials: Y
authors.lastname: Li
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
authors.forename: Huawei
authors.initials: H
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
authors.forename: Qingyou
authors.initials: Q
authors.lastname: Xia
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Zhao
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D052982:Beauveria / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development; D012831:Bombyx / Q000378:metabolism*; D002853:Chromatography, Liquid; D019286:Endopeptidase K / Q000037:antagonists & inhibitors / Q000378:metabolism; D005349:Fibroins / Q000235:genetics / Q000494:pharmacology*; D005656:Fungal Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D019476:Insect Proteins / Q000235:genetics / Q000494:pharmacology*; D007814:Larva / Q000378:metabolism; D008969:Molecular Sequence Data; D011480:Protease Inhibitors / Q000494:pharmacology; D047030:Sericins / Q000235:genetics / Q000494:pharmacology*; D047011:Silk / Q000378:metabolism; D013172:Spores, Fungal / Q000187:drug effects / Q000254:growth & development; D053719:Tandem Mass Spectrometry
chemical_list: D005656:Fungal Proteins; D019476:Insect Proteins; D011480:Protease Inhibitors; D047030:Sericins; D047011:Silk; D005349:Fibroins; D019286:Endopeptidase K