Central component of the receptor complex responsible for the recognition and translocation of cytosolically synthesized mitochondrial preproteins (By similarity). Together with tomm-22 functions as the transit peptide receptor at the surface of the mitochondrion outer membrane and facilitates the movement of preproteins into the translocation pore (PubMed:21264209). Forms part of the preprotein translocase complex of the outer mitochondrial membrane (TOM complex). RNAi-mediated knockdown results in impaired mitochondrial homeostasis with the up-regulation of the mitochondrial unfolded protein chaperone hsp-6 and impaired daf-28/insulin secretion. Belongs to the Tom20 family.