THE NUCLEOTIDE-SEQUENCE OF THE FUSION PROTEIN GENE OF THE PESTE DES PETITS RUMINANTS VIRUS - THE LONG UNTRANSLATED REGION IN THE 5'-END OF THE F-PROTEIN GENE OF MORBILLIVIRUSES SEEMS TO BE SPECIFIC TO EACH VIRUS

cDNA corresponding to the fusion protein (F) gene of the vaccine strain of peste des petits ruminants virus (PPRV) was cloned and sequenced. The gene was 2321 nucleotides long excluding the poly(A) tail. As with other morbilliviruses, it had a long G/C rich stretch of about 525 nucleotides. There was no start codon before position 489 in the nucleotide sequence. From the 489th nucleotide to the 549th nucleotide, there were 4 ATG codons, two of which were in frame. The fourth ATG codon was in the best context to act as a start codon for encoding a protein which will be composed of 546 amino acids with a predicted molecular weight of 59,310 Da. The comparison of the nucleic acid sequences of different morbillivirus F-protein genes revealed that the S-end sequence of the mRNA is specific to each virus. This sequence contains a long stretch of nucleotides rich in G/C content. When protein sequences were compared, it appears that, during evolution, substitutions in amino acids occurred in the F-protein of morbilliviruses such that the structure required for the fusion activity remains unchanged. These substitutions appear to have only occurred in the leader and the membrane anchor sequences, probably as an adaptation of the protein to the host cell.