9.A.58 The Maintenance of Mitochondrial Morphology (MMM) Family The MMM proteins are components of ERMES/MDM complexes, which serve as a molecular tethers to interconnect the endoplasmic reticulum and mitochondria. Components of this complex are involved in the control of mitochondrial shape and protein biogenesis and may function in phospholipid exchange. The MDM12-MMM1 subcomplex functions in the major beta-barrel assembly pathway that is responsible for biogenesis of all outer membrane beta-barrel proteins, and acts in a late step after the SAM complex. The MDM10-MDM12-MMM1 subcomplex further acts in the TOM40-specific pathway after the action of the MDM12-MMM1 complex. These complexes are essential for establishing and maintaining the structure of mitochondria and for the maintenance of mtDNA nucleoids (Burgess et al. 1994; Boldogh et al. 1998; Hobbs et al. 2001; Meisinger et al. 2007). These proteins are believed to be members of the TULIP superfamily (see also TC# 1.C.40 and 9.A.57) (Alva and Lupas 2016).
References:
Alva, V. and A.N. Lupas. (2016). The TULIP superfamily of eukaryotic lipid-binding proteins as a mediator of lipid sensing and transport. Biochim. Biophys. Acta. [Epub: Ahead of Print]
Boldogh, I., N. Vojtov, S. Karmon, and L.A. Pon. (1998). Interaction between mitochondria and the actin cytoskeleton in budding yeast requires two integral mitochondrial outer membrane proteins, Mmm1p and Mdm10p. J. Cell Biol. 141: 1371-1381.
Burgess, S.M., M. Delannoy, and R.E. Jensen. (1994). MMM1 encodes a mitochondrial outer membrane protein essential for establishing and maintaining the structure of yeast mitochondria. J. Cell Biol. 126: 1375-1391.
Hobbs, A.E., M. Srinivasan, J.M. McCaffery, and R.E. Jensen. (2001). Mmm1p, a mitochondrial outer membrane protein, is connected to mitochondrial DNA (mtDNA) nucleoids and required for mtDNA stability. J. Cell Biol. 152: 401-410.
Kornmann, B., E. Currie, S.R. Collins, M. Schuldiner, J. Nunnari, J.S. Weissman, and P. Walter. (2009). An ER-mitochondria tethering complex revealed by a synthetic biology screen. Science 325: 477-481.
Meisinger, C., S. Pfannschmidt, M. Rissler, D. Milenkovic, T. Becker, D. Stojanovski, M.J. Youngman, R.E. Jensen, A. Chacinska, B. Guiard, N. Pfanner, and N. Wiedemann. (2007). The morphology proteins Mdm12/Mmm1 function in the major β-barrel assembly pathway of mitochondria. EMBO. J. 26: 2229-2239.
Examples:
TC#	Name	Organismal Type	Example
9.A.58.1.1	The TULIP complex is a major mediator of lipid sensing and transport in eukaryotes (Alva and Lupas 2016). Component of the ERMES/MDM complex, which serves as a molecular tether to connect the endoplasmic reticulum and mitochondria include MMM1, MMM2 (MDM34), MDM10 and MDM12. This complex is involved in the control of mitochondrial shape and protein biogenesis and may function in phospholipid exchange. MDM34 (MMM2) is required for the interaction of the ER-resident membrane protein MMM1 and the outer mitochondrial membrane-resident beta-barrel protein MDM10. MDM12 is required for the interaction of MMM1 and the outer mitochondrial membrane-resident beta-barrel protein MDM10. The MDM12-MMM1 subcomplex functions in the major beta-barrel assembly pathway that is responsible for biogenesis of all mitochondrial outer membrane beta-barrel proteins, and acts in a late step after the SAM complex (TC# 1.B.33). The MDM10-MDM12-MMM1 subcomplex further acts in the TOM40-specific pathway (TC# 1.B.8) after the action of the MDM12-MMM1 complex (Meisinger et al. 2007). Discrete sites of close apposition between ER and mitochondria may facilitate interorganelle calcium and phospholipid exchange (Kornmann et al. 2009). See family description for more details and additional references.		The TULIP complex of Sacharomyces cerevisiae MMM1, 426 aas and 2 TMSs. May contain C2 Ca2+-binding domains homologous to protein with TC# 9.A.57.1.3) MMM2 (MDM34), 459 aas and 0 TMSs MDM10, 493 aas and 0 TMSs MDM12, 271 aas and 0, 1, or 2 TMSs

Examples:
TC#	Name	Organismal Type	Example