9.B.216 The MICOS Complex Component, Mic60 (Mic60) Family 

Mic60 is a component of the MICOS complex, a large protein complex of the mitochondrial inner membrane that plays crucial roles in the maintenance of cristae junctions, inner membrane architecture, and formation of contact sites to the outer membrane. Mic60 promotes protein import via the mitochondrial intermembrane space assembly (MIA) pathway (Rabl et al. 2009; von der Malsburg et al. 2011; Hoppins et al. 2011). 

The MICOS complex may mediate the extensive exchange of phospholipids with other cellular organelles such as the endoplasmic reticulum (ER) and vacuolar membranes in yeast. These transfers of phospholipids are thought to occur by a non-vesicular pathway at contact sites between two closely apposed membranes (Michaud et al. 2016). Plastids are able to transfer lipids to mitochondria during phosphate starvation. In Arabidopsis thaliana, a large lipid-enriched complex is called the mitochondrial transmembrane lipoprotein (MTL) complex. The MTL complex contains proteins located in the two mitochondrial membranes, conserved in all eukaryotic cells, such as the TOM complex and AtMic60. Michaud et al. 2016 demonstrated that AtMic60 contributes to the export of phosphatidylethanolamine from mitochondria and the import of galactoglycerolipids from plastids during phosphate starvation. Furthermore, AtMic60 promotes lipid desorption from membranes, likely as an initial step for lipid transfer, and binds to Tom40, suggesting that AtMic60 could regulate the tethering between the inner and outer membranes of mitochondria.


 

References:

Alkhaja, A.K., D.C. Jans, M. Nikolov, M. Vukotic, O. Lytovchenko, F. Ludewig, W. Schliebs, D. Riedel, H. Urlaub, S. Jakobs, and M. Deckers. (2012). MINOS1 is a conserved component of mitofilin complexes and required for mitochondrial function and cristae organization. Mol. Biol. Cell 23: 247-257.

Cho, B., H.M. Cho, Y. Jo, H.D. Kim, M. Song, C. Moon, H. Kim, K. Kim, H. Sesaki, I.J. Rhyu, H. Kim, and W. Sun. (2017). Constriction of the mitochondrial inner compartment is a priming event for mitochondrial division. Nat Commun 8: 15754.

Michaud, M., V. Gros, M. Tardif, S. Brugière, M. Ferro, W.A. Prinz, A. Toulmay, J. Mathur, M. Wozny, D. Falconet, E. Maréchal, M.A. Block, and J. Jouhet. (2016). AtMic60 Is Involved in Plant Mitochondria Lipid Trafficking and Is Part of a Large Complex. Curr. Biol. 26: 627-639.

Ott, C., E. Dorsch, M. Fraunholz, S. Straub, and V. Kozjak-Pavlovic. (2015). Detailed analysis of the human mitochondrial contact site complex indicate a hierarchy of subunits. PLoS One 10: e0120213.

Tarasenko, D., M. Barbot, D.C. Jans, B. Kroppen, B. Sadowski, G. Heim, W. Möbius, S. Jakobs, and M. Meinecke. (2017). The MICOS component Mic60 displays a conserved membrane-bending activity that is necessary for normal cristae morphology. J. Cell Biol. 216: 889-899.

Examples:

TC#NameOrganismal TypeExample
9.B.216.1.1

Mic60 (AIM28, FCJ1, FMP13) of 540 aas.  May be involved in vesicle-independent lipid transfer between organelles such as mitochondria, chloroplasts and the endoplasmic reticulum (Michaud et al. 2016).

Mic60 of Saccharomyces cerevisiae

 
9.B.216.1.2

Component of the mitochondrial contact site and cristae organizing system (MICOS) complex, Mic60 of 550 aas.

Mic60 of Schizosaccharomyces pombe (Fission yeast)

 
9.B.216.1.3

Uncharacterized protein; Mic70 homologue; plays roles in the formation of contact sites to the outer membrane.

UP of Dictyostelium discoideum (Slime mold)

 
9.B.216.1.4

MICOS complex component, MIC60, of 758 aas and 1 N-terminal TMS. It is a determining factor for membrane curvature with the formation of cristae (Tarasenko et al. 2017).  Homologues of this protein are found in α-proteobacteria, the persumed evolutionary source of this mitochondrial protein (Alkhaja et al. 2012). It may catalyze transfer of lipids from the membranes of mitochondra to those of other organelles.  At the ultrastructural level, mutant mitochondria display loss of inner membrane organization. MINOS1/Mio10 in yeast is a constituent of Mitofilin/Fcj1 complexes in both human and yeast mitochondria (Alkhaja et al. 2012). In human mitochondria, the inner membrane MICOS complex interacts with the outer membrane sorting and assembly machinery (SAM) complex, to form the mitochondrial intermembrane space bridging complex (MIB) (Ott et al. 2015). May play a role in mitochondrial division (Cho et al. 2017).

MIC60 of Homo sapiens

 
9.B.216.1.5

MIC60 of 575 aas and one N-terminal TMS.

MIC60 of Galdieria sulphuraria (Red alga)

 
9.B.216.1.6

Mic60, a MICOS compex subunit , of 650 aas and 1 TMSs.  The MICOS complex seems to mediate lipid transfer from the chloroplast to the mitochondrion via a non-vesicular lipid trafficking pathway at membrane contact sites (Jouhet et al. 2019).

Mic60 of Arabidopsis thaliana