Figure 8.

The functional interplay of m-AAA and rhomboid protease during Ccp1 processing. (A) The hydrophobic sorting signal (black box) triggers insertion of newly imported Ccp1 into the mitochondrial inner membrane. The m-AAA protease mediates the ATP-dependent dislocation of the hydrophobic segment from the membrane, making the second processing site (white box) accessible for the rhomboid protease Pcp1. (B) A reduced hydrophobicity of the sorting signal of mutant Ccp1 facilitates the passive dislocation of Ccp1 preproteins from the membrane and allows m-AAA protease-independent maturation by rhomboid.