Hydrophobicity profile of the wt ORF50 protein, using the presentation of Kyte and Doolittle (8). The x-axis represents a set of successive seven-residue windows along the entire amino acid sequence. The y-axis represents Kyte and Doolittle’s ‘‘hydropathy’’ sum for each of the seven residues. A positive index indicates a hydrophobic region. Two dotted lines delimit the boundaries of the deleted region in the V60 strain.