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. Ubiquitously expressed, but highly expressed in the pharyngeal muscles, the nerve ring, the intestine, gonadal sheath and in the tail hypodermis. Mutants arrest during the larval developmental stage. Impaired mitochondrial homeostasis with the up-regulation of the mitochondrial unfolded protein chaperone hsp-6. RNAi-mediated knockdown results in embryonic lethality or larval lethality between the L1 and L3 stage of larval development. Surviving progeny are growth retarded. No localization of the mitochondrial targeted protein nnt-1 to the mitochondria of intestinal cells. Belongs to the Tom40 family.