FIGURE 4.

Schematic representation of mitochondrial FtsH complexes. The i-AAA is a homocomplex facing the intermembrane space, the m-AAA is a heterocomplex (blue and bronze) facing the mitochondrial matrix. Both complexes are modeled using the cryo-EM structure of yeast m-AAA (Lee et al., 2011). The unassembled F_oa (orange cylinders) subunit of respiratory complex V (PDB: 6CP6) is a membrane protein substrate of m-AAA. MrpL32 (red cylinders) is a subunit of the mitochondrial ribosome (PDB: 5MRC), which consists of protein (yellow) and RNA (purple-gray) components. MrpL32 is a soluble substrate that requires post-translational modification by m-AAA. The proteins are scaled using the membrane width as reference. The yellow reference rulers represent the dimension (unit: Å) of the Inertia Axis Aligned Bounding Box (IAAB) for the respective protein, which are calculated by Guardado-Calvo’s Python scripts for pymol (https://pymolwiki.org/index.php/Draw_Protein_Dimensions).