Three dimensional morphology of rabies virus studied by cryo-electron tomography.

The rabies virus (RABV) continues to be a worldwide health problem. RABV contains a single-stranded RNA genome that associates with the nucleoprotein N. The resulting ribonucleoprotein complex is surrounded by matrix protein M, lipid bilayer and glycoprotein G. RABV was reported to organize in bullet-like virions, but the role of each viral component in adopting this morphology is unclear. We present here a cryo-electron tomography study of RABV showing additional morphologies consisting in bullet-like virions containing a tubular, lipidic appendage having G-protein at its apex. In addition, there was evidence for an important fraction of pleomorphic particles. These pleomorphic forms differed in the amount of membrane-associated M-, M/N-protein providing interesting insight into its role in viral morphogenesis. In the absence of membrane-associated M-, M/N-protein viral morphology was almost spherical. Other images, showing straight membrane portions, correlate with the M-protein recruitment at the membrane independently of the presence of the G-protein. The viral membrane was found to contain a negative net charge indicating that M-, M/N-protein-membrane charge attraction drives this interaction.