Recombinant expression of hepatitis A virus protein 3A: interaction with membranes

The function of hepatitis A virus (HAV) protein 3A and its structural requirements were studied in vitro and in a bacterial expression system by comparing the polypeptide precursor 3AB derived from a cytopathogenic strain with that of an attenuated strain. Although the precursor polypeptides 3AB of both HAV strains bind to microsomal membranes after translation in vitro they differ in inducing membrane permeability when expression is induced in bacteria. Intake and release of macromolecules was dramatically increased when 3AB of the cytopathogenic strain was expressed. Amino acid sequence alignments suggest that membrane binding might be due to a hydrophobic stretch near the C-terminus of 3A found in all picornaviruses whereas the ability to induce permeability of E. coli membranes is determined by an amphipathic helix formed at the N-terminus of 3A of HAVFG.