Comparisons between the Primary Structure of the Coat Proteins of Turnip Yellow Mosaic Virus and Eggplant Mosaic Virus

Comparison of the primary structures of eggplant mosaic virus (EMV) and turnip yellow mosaic virus (TYMV) coat proteins shows that 32% of their amino acids are conserved. Alignment of the two sequences requires only one deletion near the N terminus and two insertions at the C terminus of TYMV coat protein. Although the coat protein of EMV is on average less hydrophobic than that of TYMV, structural predictions yield fairly similar conformations for the two proteins, apart from the N terminus. Neither coat protein possesses an accumulation of basic residues able to form the strong ionic RNA-protein interactions observed in serveral other isometric viruses. The nature of the amino acid exchanges seems to be different from that seen in families of homologous proteins. The highly conserved regions encompass a (probably weak) potential RNA-protein interaction site. Implications for the structure and stability of small isometric viruses are discussed.