Mapping of the tobacco vein mottling virus VPg cistron.

The location of the cistron encoding the genome-linked protein (VPg) in the potyvirus tobacco vein mottling virus (TVMV) was investigated. Precipitation of 125I-labeled VPg with anti-tobacco etch virus 49K nuclear inclusion protein antiserum (which reacts with the NIa nuclear inclusion protein of TVMV) indicated that the TVMV VPg is immunologically related to NIa. Lysyl residues were found to be present at positions 2, 11, and 16 of the amino-terminal region of the VPg. A search of the TVMV polyprotein sequence for this distribution of lysyl residues revealed a unique location beginning at amino acid residue 1801, the proposed amino-terminus of the NIa protein.