Figure 3.

Modeling and quantification of mitochondrial protein import

(A) Overview of the import pathways represented in the model. The translocase of the outer membrane (TOM) serves as the main point of entry for the vast majority of proteins. Import of ∼70% of mitochondrial proteins synthesized with cleavable positively charged N-terminal presequences, follows the presequence pathway mediated by the translocase of the inner membrane 23 (TIM23) complex. Import of the presequences, that are cleaved off by mitochondrial matrix processing protease (MPP) upon import (Yang et al., 1988), is driven by the membrane potential (Δѱ) (Truscott et al., 2001) and depending on the specific signals in the protein, the protein is either laterally inserted into the membrane in a Δѱ-dependent manner (van der Laan et al., 2007) or further imported into the matrix, driven by ATP hydrolysis by the presequence translocase-associated motor (PAM) (Horst et al., 1997). Intermembrane space proteins containing specific cysteine motifs forming disulfide bridges are imported by the mitochondrial intermembrane space assembly (MIA). Mitochondrial carriers are imported by the translocase of the inner membrane 22 (TIM22) complex, assisted by TIM chaperones.

(B) Comparison of predicted abundance of the protein import machinery, before and after curation of k_cat values, to proteomics data at a growth rate of 0.1 h⁻¹ (Lahtvee et al., 2017).

(C and D) Predicted abundances of the protein import machinery at increasing growth rate and maximum growth rate.

See also Figures S1 and S2