Cristae formation

Cristae formation Cristae are invaginations of the inner mitochondrial membrane that extend into the matrix and are lined with cytochrome complexes and F1Fo ATP synthase complexes. Cristae increase the surface area of the inner membranes allowing greater numbers of respiratory complexes. Cristae are also believed to serve as "proton pockets" to generate localized regions of higher membrane potential. The steps in the biogenesis of cristae are not yet completely elucidated (reviewed in Zick et al. 2009) but the formation of the Mitochondrial Contact Site and Cristae Organizing System (MICOS, formerly also known as MINOS, reviewed in Rampelt et al. 2016, Kozjak-Pavlovic 2016, van der Laan et al. 2016) and localized concentrations of cardiolipin are known to define the inward curvature of the inner membrane at the bases of cristae. MICOS also links these regions of the inner membrane with complexes (the SAM complex and, in fungi, the TOM complex) embedded in the outer membrane. CHCHD3 (MIC19) and IMMT (MIC60) subunits of MICOS also interact with OPA1 at the inner membrane (Darshi et al. 2011, Glytsou et al. 2016).
Formation of dimers or oligomers of the F1Fo ATP synthase complex causes extreme curvature of the inner membrane at the apices of cristae (reviewed in Seelert and Dencher 2011, Habersetzer et al. 2013). Defects in either MICOS or F1Fo ATP synthase oligomerization produce abnormal mitochondrial morphologies.