Fig. 2

Schematic representation of the mitochondrial protein import complexes of Saccharomyces cerevisiae and their subunits shared with the studied amoebozoans. The TOM complex contains a channel-forming subunit (Tom40), receptors for precursor proteins (Tom20 and Tom70), an internal receptor, which also maintains the complex architecture (Tom22), and modulators of the complex assembly and stability (Tom5, Tom6, and Tom7). The TOB/SAM complex contains a channel-forming subunit (Tob55/Sam50), which cooperates with Sam35/Tob38 and Sam37/Mas37 in the recognition, transport, and integration of β-barrel proteins into the membrane. The TIM22 complex is composed of a channel-forming subunit (Tim22) and three modulators of the complex stability and activity, i.e. Tim18, Tim54, and Sdh3. The TIM23 complex consists of Tim50 (which functions as a receptor in the initial stages of precursor translocation), Tim23 and Tim17 (forming a channel within the complex), as well as Tim21 and Mgr2 (suggested to play an important role in the cooperation with the respiratory chain) The absence of Mgr2 enables the TIM23 complex interaction with the PAM complex. The complex consists of mtHsp70, Tim44, and a group of co-chaperones and supporting proteins, i.e. Pam16 (Tim16), Pam18 (Tim14), the nucleotide exchange factor Mge1, Pam17 and Tim15. The OXA complex is formed by Oxa1, which is thought to cooperate with its paralog, Oxa2, serving as an auxiliary subunit. The MIA complex consists of two proteins, namely the oxidoreductase Mia40 and sulfhydryl oxidase Erv1. *, subunits found only for slime molds; **, a subunit found only for A. castellanii; AIF – apoptosis inducing factor