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The mitochondrial Sorting and Assembly Machinery (SAM) includes SAM50, Tom37 (Mas37; Sam37), Tom13 (Mim1), Mim2, and porin; see 3.A.8 (Paschen et al., 2005). The MIM complex can assemble N- and C-terminal α-helical anchor proteins. SAM and TOM insert β-barrel proteins in the outer mitochondrial membrane (Stojanovski et al., 2007). Mim1 (Tom13) is required for the biogenesis of the beta-barrel protein Tom40 and also for membrane insertion and assembly of signal- and C-terminally-anchored Tom receptors (Becker et al., 2008; 2011). It has cation-selective ion transport activity (Checchetto and Szabo 2018; Krüger et al. 2017). Tom7 regulates Mdm10-mediated assembly of the mitochondrial import channel protein Tom40 (Yamano et al., 2010). Homologous Omp85 proteins are essential for membrane insertion of β-barrel precursors. Precursors are apparently threaded through the Omp85-channel interior and exit laterally. Höhr et al. 2018  mapped the interaction of a precursor in transit with the mitochondrial Omp85-channel Sam50 in the native membrane environment. The precursor is translocated into the channel interior, interacts with an internal loop, and inserts into the lateral gate by β-signal exchange. Transport through the Omp85-channel interior followed by release through the lateral gate into the lipid phase represents a basic mechanism for membrane insertion of β-barrel proteins (Höhr et al. 2018). The TOM and SAM complexes cooperate in the import of beta-barrel proteins, whereas the mitochondrial import  (MIM) complex (Mim1/Mim2/porin) inserts precursors of multi-spanning alpha-helical proteins. Single-spanning proteins constitute more than half of the integral outer membrane proteins. Doan et al. 2020 reported that the yeast MIM complex promotes the insertion of proteins with N-terminal (signal-anchored) or C-terminal (tail-anchored) membrane anchors. The MIM complex exists in three dynamic populations. MIM interacts with TOM to accept precursor proteins from the receptor Tom70. Free MIM complexes insert single-spanning proteins that are imported in a Tom70-independent manner. Finally, coupling of MIM and SAM promotes early assembly steps of TOM subunits. Thus, the MIM complex is a major and versatile protein translocase of the mitochondrial outer membrane (Doan et al. 2020).

Accession Number:Q08176
Protein Name:Mim1 aka Tom13
Molecular Weight:12758.00
Species:Saccharomyces cerevisiae (Baker's yeast) [4932]
Number of TMSs:1
Location1 / Topology2 / Orientation3: Mitochondrion outer membrane1
Substrate proteins

Cross database links:

RefSeq: NP_014616.1   
Entrez Gene ID: 854131   
Pfam: PF08219   
KEGG: sce:YOL026C   

Gene Ontology

GO:0031307 C:integral to mitochondrial outer membrane
GO:0005515 F:protein binding
GO:0006461 P:protein complex assembly
GO:0006626 P:protein targeting to mitochondrion

References (5)

[1] “The nucleotide sequence of Saccharomyces cerevisiae chromosome XV.”  Dujon   9169874
[2] “Approaching a complete repository of sequence-verified protein-encoding clones for Saccharomyces cerevisiae.”  Hu   17322287
[3] “Two novel proteins in the mitochondrial outer membrane mediate beta-barrel protein assembly.”  Ishikawa   15326197
[4] “Exploration of essential gene functions via titratable promoter alleles.”  Mnaimneh   15242642
[5] “Mim1, a protein required for the assembly of the TOM complex of mitochondria.”  Waizenegger   15608614

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