Involved in mitochondrial distribution and morphology. Mediates the import of UPS1, UPS2 and UPS3, 3 atypical mitochondrial intermembrane space (IMS) proteins lacking the two major IMS-targeting signals, into the intermembrane space. The UPS1:MDM35 complex mediates the transfer of phosphatidic acid (PA) between liposomes and probably functions as a PA transporter across the mitochondrion intermembrane space (PubMed:26071602, PubMed:26071601, PubMed:26235513). Phosphatidic acid import is required for cardiolipin (CL) synthesis in the mitochondrial inner membrane (PubMed:26071602). Interacts with UPS1, UPS2 and UPS3. Present with 3870 molecules/cell in log phase SD medium. Belongs to the TRIAP1/MDM35 family.