Plays a role in the inhibition of host innate immune response by targeting the mitochondrial-associated adapter MAVS. Mechanistically, usurps the E3 ligase ITCH to trigger the degradation of MAVS, TRAF3, and TRAF6. In addition, causes mitochondrial elongation by triggering ubiquitination and proteasomal degradation of dynamin-like protein 1/DNM1L. Homodimer. Interacts with host XPO1; this interaction mediates protein ORF9b export out of the nucleus (PubMed:21637748). Interacts with host MAVS (PubMed:25135833). Interacts with protein ORF6 (PubMed:22820404). Binds non-covalently to intracellular lipid bilayers. The gene encoding this protein is included within the N gene (alternative ORF). Belongs to the coronavirus group 2 protein 9b family.