Component of the ERMES/MDM complex, which serves as a molecular tether to connect the endoplasmic reticulum (ER) and mitochondria (PubMed:11907266, PubMed:14981098). Components of this complex are involved in the control of mitochondrial shape and protein biogenesis, and function in nonvesicular lipid trafficking between the ER and mitochondria (PubMed:27469264). MDM34 is required for the interaction of the ER-resident membrane protein MMM1 and the outer mitochondrial membrane-resident beta-barrel protein MDM10 (By similarity) (PubMed:19556461). Component of the ER-mitochondria encounter structure (ERMES) or MDM complex, composed of MMM1, MDM10, MDM12 and MDM34. The ERMES/MDM complex localizes to a few discrete foci (around 10 per single cell), that represent mitochondria-endoplasmic reticulum junctions. These foci are often found next to mtDNA nucleoids. Lacks alpha-helical transmembrane segments, suggesting that it resides in the membrane via beta-sheet conformations similar to those predicted for other outer membrane proteins and porin. The SMP-LTD domain is a barrel-like domain that can bind various types of glycerophospholipids in its interior and mediate their transfer between two adjacent bilayers. Ubiquitinated by a SCF (SKP1-CUL1-F-box protein) E3 ubiquitin-protein ligase complex containing the F-box protein MDM30. Ubiquitination is important for mitochondrial integrity. Present with 377 molecules/cell in log phase SD medium. Belongs to the MDM34 family.