Proposition Of A 3-Dimensional Representation Of The Constitutive Protein Of The Hepatitis-B Surface-Antigen Particles

Hepatitis B surface antigen particles are composed of the major viral envelope
protein, the S protein, embedded into a lipid shell. The description of the
folding of this protein within the particle membrane could provide helpful
information for replacing surface-exposed protein domains by foreign sequences
without destabilizing the particle structure. Since the crystallization of the
protein in its lipid environment remains inaccessible in the near future,
alternative approaches had to be envisaged. We combine here the available
experimental structural and topological data with a conformational procedure to
identify membrane-associated domains of the HBsAg protein and to propose a
three-dimensional description of their assembly within the particle membrane. The
proposed protein structure is composed of four membrane-spanning helices and an
amphipatic helix located on the inner surface membrane. The transmembrane helices
are assembled into a highly hydrophobic complex in which no access to the water
environment is allowed. The approach could be extended to other
membrane-associated proteins.