Interviral homologies of the 30K proteins of tobamoviruses.

The 30K protein of tobacco mosaic virus was recently confirmed to be involved in cell-to-cell movement of the virus. To characterize common structural features of the 30K protein, the nucleotide sequence of the 30K protein gene of cucumber green mottle mosaic virus (CGMMV, a member of the tobamoviruses) RNA has been determined. The CGMMV 30K protein is composed of 264 amino acids with a calculated molecular weight of 28,800. Comparisons among the 30K proteins of tobamoviruses show that the 30K proteins are composed of a rather conserved N-terminal two-thirds and a less-conserved C-terminal one-third. The N-terminal two-thirds contain two particularly well-conserved sequences, one of which contains amino acid substitutions that result in temperature-sensitive cell-to-cell movement. The C-terminal region is further divided into three subregions by distribution of charged amino acid residues.