Study On The F Protein Of Baculovirus

F protein is an important baculovirus protein, which is divided into twocategories, Fa and Fb. Fa is a groupⅡNPV budding virus membrane protein.Sprouting and the baculovirus infection can spread alternative GP64 importantfunction; Fb GroupⅠNPV is a transmembrane protein, GP64 have been guessed toreplace the function of Fb in the evolutionary homology. CbNPV (Clanis bilineataNPV) is a new discovered baculovirus of our laboratory; AcNPV (Autographacalifionica NPV) and BmNPV (Bombyx mori NPV) is a typical groupⅠNPV. Tounderstand the nature, characteristics and functions of Fa and Fb, and to know thefunctional relationship between the GP64 and Fa, Fb, this paper studies the three virusby analyzing gene sequences, real time PCR and fluorescent protein tracer method toconducted a preliminary study to Fa, Fb and GP64 protein. The main conclusions arefollowed:1．The CbNPV Fa gene was analized systematically first. ORF of CbNPV Fagene has 2109 nucleotides,encoding 702 amino acids, and the molecular weight of itis about 80．69kDa. It has early and late promoter; containing characters of synexin.These structural features are very similar to the GP64 protein.2．CbNPV F protein and several representative Fa, Fb and GP64 proteinhomology analysis. The results showed that the homology between CbNPV F proteinand the other Fa is the number of 32．9%～61．8%. So the CbNPV F protein shouldbelong to Fa family; the homology between CbNPV F protein and the GP64 or thehomology between it and Fb is poor.3．The homology to Fa, Fb and GP64 was analyzed and phylogenetic tree wasmade. Analysis shows that the homology between some kinds of NPV's Fa and theGP64 lies in 25%～35%, and all the others(include the homology between Fb andGP64) are less than 25%, which showed that the gp64 was come from outside. Thepromoter region of Fa, Fb and GP64 of which the genome sequences of NPV had known, was analyzed. And the result showed that three of all had early and latefactors. So Fb is not evolution redundant gene but an important function genes.4．Expression of AcNPV, BmNPV Fb and gp64 were displayed by the real-timequantitative PCR and identified by semi-quantitative PCR. The result showed that Fbis not only expressing but also showing a pattern of expression changes, which proofthat Fb is not the evolution Redundancy gene but an important function gene. Theoverall trend of Fb and gp64 expression is similar. However, the expression of Fb todifferent types of baculovirus has a different change in degrees to relative gp64．Theexpression of gp64 is far more than that of Fb, and compared with gp64 theexpression of Fb of different types of baculovirus has a greater difference. So, itsupposed that in GroupINPV Fb protein had no functional correlation with GP64protein. However, the function of Fb protein correlated with the characters to differenttypes of baculovirus himself.5．BmNPV Fb can be expressed in silkworm cells only with the role of BmNPVactivating factor. Furthermore Fb has no signal peptide, and therefore has a ratherdifferent functions with Fa.6．CbNPV Fa and ie-1 gene could not express in BmN and Tn5 cells but couldexpress in Sf9 and Spli cells.