Single amino acid substitution in 30K protein of TMV defective in virus transport function

Involvement of the tobacco mosaic virus (TMV) coded 30K protein in a virus transport function within the infected plant has been suggested. Previously a temperature sensitive mutant, TMV Ls 1, that is defective in cell-to-cell movement at a restrictive temperature, was reported. To demonstrate a relationship between the 30K protein and the transport function, the nucleotide sequences of the 30K and coat protein cistrons of the mutant, TMV Ls 1, and the wild type, TMV L (tomato strain) were compared. A single base substitution which causes replacement of a proline codon in the L strain by a serine codon was found in the Ls 1 mutant. Results support the notion that the 30K protein is responsible for the virus transport function.