Site-directed mutagenesis of hepatitis A virus protein 3A: effects on membrane interaction.

Due to a stretch of hydrophobic amino acids, protein 3A of hepatitis A virus (HAV) has been suggested to act as a membrane anchor or a carrier of the genome-linked protein 3B (VPg) during viral RNA synthesis. Mutagenesis analysis was performed in order to elucidate the role of the N- and C-terminal tracts of protein 3A in cell membrane interaction. Expression of the mutated proteins in E. coli cells demonstrated that the presence of positively charged residues at the C-terminus is not required for membrane anchoring. Changes in the primary sequence involving charged amino acids at the N- and C-termini critically influenced the ability of the protein 3A of a cytopathic strain of HAV to change bacterial membrane permeability. This result demonstrates the strict correlation between the structure and pore-forming potential of HAV protein 3A.