Effects of Ectodomain Non-conservative Sequences of F1 Protein of Paramyxoviruses on the Specific Membrane Fusion
To understand the effects of ectodomain non-conservative sequences of F1 protein on the specific interaction with its homologous hemagglutinin-neuraminidase (HN), site-directed mutagenesis was used to obtain mutants containing new enzymatic sites and the other four non-conservative segments (NDV F-1, hPIV F-1, NDV F-2 and hPIV F-2) were obtained by cutting mutant F genes with these new enzymes. Gene recombination was used to get chimeric F protein NDV-C1 and hPIV-C1 by exchanging NDV F-1 and hPIV F-1 each other, and NDV-C2 and hPIV-C2 were obtained by the same way. All the mutants and chimeric F proteins were co-expressed in eukaryocytes with their homologous HN DNA or heterogenous HN DNA. The fusion functions were assayed by Giemsa staining and reporter gene method, the expression of F protein was assayed by fluorescence-activated cell sorter (FACS). Results of experiment were that the mutants of paramyxoviruses fusion proteins had the same functions as their relevant wild types. Chimeric F proteins NDV-C1 and hPIV-C1 had 76.34% and 65.82% of fusion activities, and chimeric F proteins NDV-C2 and hPIV-C2 had 96.25% and 93.78% of fusion activities, respectively, as compared with their relevant wild types. The analysis of FACS indicated that all the mutants and chimeric F proteins had almost the same expression efficienciy as their relevant wild types. The results suggested that NDV F-1 and hPIV F-1 were important for their specific membrane fusion, but NDV F-2 and hPIV F-2 were not.