Structural Analysis of Rabies Virus Glycoprotein Reveals pH-Dependent Conformational Changes and Interactions with a Neutralizing Antibody.

Rabies virus (RABV), the etiological agent for the lethal disease of rabies, is a deadly zoonotic pathogen. The RABV glycoprotein (RABV-G) is a key factor mediating virus entry and the major target of neutralizing antibodies. Here, we report the crystal structures of RABV-G solved in the free form at ∼pH-8.0 and in the complex form with a neutralizing antibody 523-11 at ∼pH-6.5, respectively. RABV-G has three domains, and the basic-to-acidic pH change results in large domain re-orientations and concomitant domain-linker re-constructions, switching it from a bent hairpin conformation into an extended conformation. During such low-pH-induced structural transitions, residues located in the domain-linker are found to play important roles in glycoprotein-mediated membrane fusion. Finally, the antibody interacts with RABV-G mainly through its heavy chain and binds to a bipartite conformational epitope in the viral protein for neutralization. These structures provide valuable information for vaccine and drug design.