Channel-forming protein essential for import of protein precursors into mitochondria. Forms part of the preprotein translocase of the outer mitochondrial membrane (TOM complex). Interacts with mitochondrial targeting sequences (By similarity). Only expressed in the male germline, detected in primary spermatocytes as well as post-meiotic stages. Not detected in stem cells and spermatogonia near the tip of the testis. Belongs to the Tom40 family.