Structure of small HBV surface antigen reveals mechanism of dimer formation

Hepatitis B surface antigen (HBsAg), the only membrane protein on the HBV viral envelope, plays essential roles in HBV assembly, viral release, host cell attachment, and entry. Despite its functional and therapeutic importance, the detailed structure of HBsAg has remained enigmatic. Here, we present the core structure of HBsAg at 3.6 [A] resolution, determined using recombinant small spherical subviral particles (SVPs). The structure reveals how two HBsAg monomers interact to form a dimer, which is the basic building block of SVPs.