HBV virions and subviral particles contain variable proportions of the three co-carboxyterminal surface (glyco)-proteins: the large (LHBs), middle (MHBs) and small (SHBs) surface proteins . HBV surface proteins are products of a single open reading frame and distinguished by three domains (Figure 1). HBV comprises: preS1 (108 or 119 aa depending on the genotype) only in LHBs, preS2 (55 aa) in LHBs and MHBs, and S (226 aa) common to all three HBs proteins. The large envelope protein (LHBs) consists in 399 or 400 amino acids (aa) for most of genotypes and 389 aa for genotype D.
The envelope proteins are synthesized at the ER and show a complex transmembrane topology .
Figure 1. The S protein numbering is defined based on the HBVdb X02763 protein numbering.
Viral and cellular determinants involved in hepadnaviral entry.
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