HBV envelope proteins
HBV encodes for three envelopes proteins: SHB, MHB (PreS2+S) and LHB (PreS1+PreS2+S). MHB and LHB form heterodimers with SHB , and SHB form homodimers (Wounderlich et al. 1996) Rating=2
LHB hydrophylic PreS1-PreS2 domain is able to translocate through the membrane. It is cytoplasmic after translation, TM1 being not used as a translational signal sequence in this context. A fraction of PreS1-PreS2 domain is translocated posttranslationaly toward the extracellular space, reaching an equilibrium with 50% cytoplasmic and 50% lumenal domain. The lumenal orientated LHB proteins are implicated in receptor recognition, whereas the internally orientated plays an essential role i virus morphogenesis by interacting with the nucleocapsid (Bruss et al. 1997) Rating=3 (Poisson et al. 1997) Rating=3 and may also play a role as transcription trans-activator through PKC binding (Hildt et al. 2002) Rating=1
Comments The ability of the PreS1 domain to translocate in and out of the membrane is remarkable and unique in virology. Interestingly the second half of preS1 is intrinsically disordered. It is worth noting that the core display a similar pattern of disordered region flipping in and out of the icosahedral capsid.