The mitochondrial inner/outer membrane fusion complex, Fzo/Mgm1/Ugo1. Only the Ugo1 protein is a member of the MC superfamily, and PCD2 is a functional domain required for mitochondrial fusion. It has a single carrier domain (Coonrod et al. 2007).
The Fzo/Mgm1/Ugo1 complex of Saccharomyces cerevisiae
The mammalian mitochondrial membrane fusion complex, Mitofusin 1/2 (Mfn1)/Mfn2/Optical Atrophy Protein 1 (OPA1) complex (the equivalent of the yeast Ugo1 protein)/dynamin-related protein 1 Drp1 (Chandhok et al. 2018). Mfn1 and Mfn2 are two very similar (60% identity) GTPase dynamin-like proteins in the outer mitochondrial membrane (members of the CDD P-loop[ NTPase Family) while OPA1 is a sequence divergent GTPase in the inner membrane (Chen and Chan, 2010). Mfn2 plays roles in mitochondrial fusion and mitochondrial endoplasmic reticulum interactions (Ranieri et al. 2013; Schneeberger et al. 2013). Mfn2, when defective can give rise to Charcot-Marie-Tooth disease, diabetes, neurodegenerative diseases, obesity and vascular diseases (Chandhok et al. 2018). It may also function in insulin-dependent myogenesis (Pawlikowska et al. 2007). Drp1 (DLP1, DNM1L) mediates membrane fusion and fission through
oligomerization into membrane-associated tubular structures that wrap
around the scission site to constrict and sever the mitochondrial
membrane in a GTP hydrolysis-dependent mechanism (Smirnova et al. 2001; Taguchi et al. 2007). Sequences flanking the TMSs facilitate membrane fusion by mitofusin (Huang et al. 2017). Opa1 is a mitochondrial remodeling protein with a dual role in maintaining mitochondrial morphology and energetics by mediating inner membrane fusion and maintaining the cristae structure. This and the fusion/fission process by dynamins is described by Lee and Yoon 2018.
Mfn1/Mfn2/OPA1/Drp1 complex of Homo sapiens
Mfn1 or Fzo1B (Q8IWA4)
Mfn2, Hsg or Fzo1A (O95140)