| Summary: | 碩士 === 國立中興大學 === 微生物暨公共衛生學研究所 === 106 === Most members of the Flavivirus genus in the family of Flaviviridae, including dengue virus (DENV), West Nile virus (WNV) and Zika virus (ZIKV), infect vertebrate and arthropod hosts. These two hosts flaviviruses caused a pandemic around the world become public heathy concern so it also called medically important flaviviruses (MIFs). But in last decade, there has been a dramatic increase in the number of insect-specific flaviviruses (ISFs) discovered. ISFs can infect insects and insect cells, but they do not replicate and infect vertebrates or vertebrate cells. Some ISFs have been shown to suppress or inhibit the replication of MIFs in mosquito cells. The envelope glycoprotein (E protein) of flavivirus is an important determinant for host range or tissue tropism. But, the characteristics of ISFs E protein are still unclear. Here, comprehensive and total 37 ISF E protein sequences were collected, and analyzed and predicated with public-domain software. The phylogenic tree based on E protein amino acid sequence showed ISFs classified into two groups, classical ISFs (cISFs) and dual-host affiliated ISFs (dISFs), except Paraiso Escondido virus. The length of the E protein amino acid sequence of cISFs (426to 432 amino acids) was shorter than dISFs (491 to 504 amino acids) and MIFs (489 to 501 amino acids). The MIFs E protein is glycosylated at 1 to 2 amino acids, the potentially N-linked glycosylation sites of dISFs and cISFs were 0~2 and 1~6 amino acids, respectively. There were six conserved disulfide (SS) bonds in the MIFs E protein, the predicated SS bonds in the dISFs and cISFs E protein were 5 and 6~7 bonds, respectively. The predicated transmembrane region topology of dISFs was similar to MIFs, which contain 2 transmembrane domains, but the cISFs just contain 1 transmembrane domain. The dimer structure of ISFs E protein was predicated using SWISS-MODEL based on the resolved and best template of Japanese encephalitis virus E protein. The MIFs E protein folds into three distinct domains (domain I, II, and III), and forms tight contact dimer (higher buried surface area, BSA). The predicated structure of dISFs E protein was similar to MIFs, but the cISFs showed different characteristics, including domain folding, lower BSA, receptor binding motif and fusion loop. Overall, the dISFs were genetically close-related to MIFs, and the predicated E protein structure also shown similar features.
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