Figure 1. Mitochondrial Ultrastructure and Morphogenic Complexes.

A) Major mitochondrial compartments. Subcompartments are established by the outer membrane (OM; green) and inner membrane (IM; cyan), parsed into the inner boundary membrane (IBM) and cristae membrane (CM). Aqueous compartments include the intermembrane space (IMS) (between OM and IBM), the intracristal space (ICS) (enclosed by cristae), and matrix. Major cristae features include the crista junction (CJ) and the crista tip (CT). B-D) Assemblies that establish IM morphology. The subunits of each complex are shown for yeast (left) and for metazoans (right). B) The MICOS Complex establishes and stabilizes CJs. MICOS is composed of six (yeast) or seven (metazoan) known subunits, each named as MicX (X numbering based on molecular weight). The MIC60 subcomplex (cyan) consists of the central Mic60 (mitofilin) subunit and peripheral regulatory proteins Mic19/25, mediating a number of interactions (dashed lines) with IBM and OM proteins. The MIC10 subcomplex (green) contains the central Mic10 subunit, apolipoprotein O-related Mic26/27, which antagonistically regulate Mic10 assembly, and Mic12, which mediates MIC60-MIC10 subcomplex association. C) Mgm1/Opa1 Assemblies are GTPases that exist as long forms (l-Mgm1/l-Opa1) with an N-terminal transmembrane anchor, or as short forms (s-Mgm1/s-Opa1) that are proteolytically processed by IM proteases Pcp1 (yeast) or OMA1/YME1 (metazoan). Oligomers of l-Mgm1/l-Opa1 assemble in a cardiolipin-dependent manner to stabilize connections of cristae walls. D) The F₁F_O-ATP synthase consists of the F₁ sector [catalytic headpiece (α₃β₃) and central stalk (γ,δ,ε)] and F_O sector [rotor (c ring, a, 8), peripheral stalk (b, d, h/F6, OSCP), and supernumerary subunits (f, i/j/6.8, e, g, k)]. Homodimer assembly is mediated by subunits e, g and k (DAPIT in metazoans). Higher-order assembly occurs as extended dimer rows along cristae ridges.