The Molecular Cloning and Sequence of an Open Reading Frame Encoding for Non-Structural Proteins of Feline Calicivirus F4 Strain Isolated in Japan.

The nucleotide sequence of the 5'-end of feline calicivirus (FCV) Japanese F4 strain genome was determined. This region had 5311 bases and contained a large open reading frame (ORF1) encoding the non-structural proteins. The nucleotide sequence of the ORF1 region was highly conserved as compared with that of FCV F9 strain. When the deduced amino acid sequence of the ORF1 was compared with those of FCV F9 and CFI strains, the sequence was also highly conserved (88.9% and 88.8%, respectively). Functional motifs of the non-structural proteins were common to these strains. There were 2C polypeptide-, 3C cysteine protease- and 3D RNA-dependent RNA polymerase-like regions. The N-terminal region of 2C-like region continued upstream from the region identified by Neill [Virus Res. 17: 145-160]. Furthermore, the presence of 2B-like region was suggested in the upper stream of the 2C-like region, although the function of the region is unknown. When Kyte and Dolittle hydrophobicity profiles of the predicted amino acid sequences of the ORF1s of FCV F4 and F9 were computed and compared, both the profiles had striking similarities. In the region between residues 950-1000, there was a high rate of basic amino acid residues, suggesting that the polypeptide in this region of FCV may have a nucleic acid-binding function.