Acts as receptor of the preprotein translocase complex of the outer mitochondrial membrane (TOM complex). Recognizes and mediates the translocation of mitochondrial preproteins from the cytosol into the mitochondria in a chaperone dependent manner (PubMed:11956321, PubMed:19401463). Mediates TBK1 and IRF3 activation induced by MAVS in response to Sendai virus infection and promotes host antiviral responses during virus infection (By similarity). Forms part of the preprotein translocase complex of the outer mitochondrial membrane (TOM complex) which consists of at least 7 different proteins (TOMM5, TOMM6, TOMM7, TOMM20, TOMM22, TOMM40 and TOMM70) (By similarity). Interacts with CAPN8 (By similarity). Interacts with TRADD, TRAF6 and STING. Interacts with MAVS. Interacts with HSPA8 and HSP90AA1; both interactions are required for preprotein mitochondrial import. The interaction with HSP90AA1 is direct and mediates the association of TOMM70 with IRF3 and TBK1 (By similarity). Belongs to the Tom70 family.