Sequence analysis on nucleocapsid protein gene of velogenic chicken-origin Newcastle disease virus,F48E9 strain

The nucleocapsid protein gene of velogenic,chicken-origin,Newcastle disease virus(NDV) F48E9 was amplified by RT-PCR based on a specific pair of primers designed according to the chicken-origin NDVs NP gene sequences published at GenBank.The purified RT-PCR products were cloned onto the pMD18-T vectors,and then,the positive recombinants had been identified by PCR and enzyme digestion.The sequencing results indicated that the F48E9 NP gene had an opening read frame of 1470nt in length with a coded polypeptide of 489 amino acids. There were four highly conserved cysteines on the F48E9 strain nucleocapsid protein.The amino acids at the regions, aa 401-440 and aa 461-481,were found to vary more than the others.The sequence analysis indicated that the F48E9 strain had a nucleotide homology of 87.9%-92.3%,and the amino acid homology of 92.2%-98.0% with other NDVs.The F48E9 strain appeared to be evolutionarily independent,with only remote relationship with other NDVs.