POLYPEPTIDE 3AB OF HEPATITIS-A VIRUS IS A TRANSMEMBRANE PROTEIN

Hepatitis A virus (HAV) protein 3AB is a membrane-interacting protein containing a stretch of 21 hydrophobic amino acid residues. The nature of its membrane association was studied in detail by analysing variou s deletion mutants. In vivo and in vitro expression of the wild-type p rotein and its mutants allowed to demonstrate that the hydrophobic dom ain interacts with membranes and to define the portions essential for this feature. Furthermore, the results suggest that 3AB behaves as an integral membrane protein. Expression in Escherichia coil showed that 3AB can be isolated, in association with membranes, both in monomeric and in dimeric form. This finding was confirmed in vitro after post-tr anslational incubation of the protein with microsomal membranes. Analy sis of deletion mutants demonstrated that the dimerization region colo calises with the hydrophobic transmembrane domain, implicating that HA V 3AB could form oligomers mediated by the interaction of transmembran e alpha-helices. (C) 1998 Academic Press.