The large envelope protein exists in two topological conformations, one which is termed 'external' or Le-HBsAg and the other 'internal' or Li-HBsAg. In its external conformation the protein attaches the virus to cell receptors and thereby initiating infection. This interaction determines the species specificity and liver tropism. The large envelope protein probably also assumes fusion between virion and host membranes. In its internal conformation the protein plays a role in virion morphogenesis and mediates the contact with the nucleocapsid like a matrix protein (By similarity). Truncated S protein may be involved in translocation of pre-S domain through the virion membrane. Large internal envelope protein interacts with capsid protein. The large envelope protein is synthesized with the pre-S region at the cytosolic side of the endoplasmic reticulum and, hence will be within the virion after budding. Therefore the pre-S region is not N-glycosylated. Later a post-translational translocation of N-terminal pre-S and TM1 domains occur in about 50% of proteins at the virion surface. These molecules change their topology by an unknown mechanism, resulting in exposure of pre-S region at virion surface. Myristoylation contributes importantly to DHBV infectivity. It is most likely required for an early step of the life cycle involving the entry or uncoating of virus particles. Phosphorylated on pre-S domain for about 50% of L proteins, the L chains with internal pre-S region (Li-HBsAg). Belongs to the avihepadnavirus major surface antigen family.