Channel-forming protein essential for import of protein precursors into mitochondria. Specifically required for nnt-1 accumulation in the mitochondria and may be involved in the secretion of daf-28/insulin from the mitochondria. Required for embryonic and larval development. Forms part of the preprotein translocase complex of the outer mitochondrial membrane (TOM complex). Interacts with mitochondrial targeting sequences. Belongs to the Tom40 family.