SOM1/YEL059C-A Summary Help

Standard Name SOM1 1
Systematic Name YEL059C-A
Feature Type ORF, Verified
Description Subunit of the mitochondrial inner membrane peptidase (IMP); IMP is required for maturation of mitochondrial proteins of the intermembrane space; Som1p facilitates cleavage of a subset of substrates; contains twin cysteine-x9-cysteine motifs (1, 2, 3, 4, 5 and see Summary Paragraph)
Name Description SOrting Mitochondrial 1
Chromosomal Location
ChrV:42624 to 42400 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Gene Ontology Annotations All SOM1 GO evidence and references
  View Computational GO annotations for SOM1
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 7 genes
Classical genetics
Large-scale survey
6 total interaction(s) for 5 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 1
  • Affinity Capture-RNA: 1
  • Affinity Capture-Western: 1

Genetic Interactions
  • Dosage Rescue: 1
  • Negative Genetic: 2

Expression Summary
Length (a.a.) 74
Molecular Weight (Da) 8,415
Isoelectric Point (pI) 5.82
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrV:42624 to 42400 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Last Update Coordinates: 1996-07-31 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..225 42624..42400 1996-07-31 1996-07-31
Retrieve sequences
Analyze Sequence
S288C only
S288C vs. other species
S288C vs. other strains
External Links All Associated Seq | Entrez Gene | Entrez RefSeq Protein | MIPS | Search all NCBI (Entrez) | UniProtKB
Primary SGDIDS000002954

About mitochondrial import

While the mitochondrial genome encodes a handful of proteins, most of the hundreds of proteins that reside in the mitochondrion are encoded by nuclear genes, translated in the cytoplasm, and imported into mitochondria via a series of complex molecular machines (see 6, 7 for review). Many of the proteins imported into mitochondria are involved in respiration, which is not an essential process: S. cerevisiae is able to carry out either fermentative growth on carbon sources such as glucose, or respiratory growth on nonfermentable carbon sources such as glycerol and ethanol. However, since maintenance of the mitochondrial compartment is essential to life, mutations that completely disrupt mitochondrial import are lethal.

About the Inner Membrane Protease (IMP)

Most proteins undergo proteolytic processing upon import into mitochondria, and multiple proteases cleave different subsets of these proteins. The Inner Membrane Protease, IMP, processes some proteins that are translocated from the mitochondrial matrix into the intermembrane space. IMP consists of three subunits: Imp1p, Imp2p, and Som1p (3). Both Imp1p and Imp2p are catalytic subunits and share 25% identity, though each protein has distinct substrate specificities (8, 9, 10). Among the substrates of Imp1p are the precursors to NADH-cytochrome b5 reductase (Mcr1p), cytochrome b2 (Cyb2p), FAD-dependent glycerol-3-phosphate dehydrogenase (Gut2p), and the mitochondrially encoded subunit II of cytochrome c oxidase (Cox2p), while the only known substrate of Imp2p is cytochrome c1 (Cyt1p; 3, 1, 8, 11). In addition to its catalytic activity, Imp2p is also required for the stable expression of Imp1p (8). Som1p is a noncatalytic subunit that has been proposed to have a role in substrate recognition and correct functioning of Imp1p; it is required for processing of Cox2p and Mcr1p, and the som1 mutation reduces processing of Cyb2p (3).

Last updated: 2009-03-17 Contact SGD

References cited on this page View Complete Literature Guide for SOM1
1) Esser K, et al.  (1996) SOM 1, a small new gene required for mitochondrial inner membrane peptidase function in Saccharomyces cerevisiae. Mol Gen Genet 252(4):437-45
2) Bauerfeind M, et al.  (1998) The Saccharomyces cerevisiae SOM1 gene: heterologous complementation studies, homologues in other organisms, and association of the gene product with the inner mitochondrial membrane. Mol Gen Genet 257(6):635-40
3) Jan PS, et al.  (2000) Som1, a third component of the yeast mitochondrial inner membrane peptidase complex that contains Imp1 and Imp2. Mol Gen Genet 263(3):483-91
4) Liang H, et al.  (2004) Cargo sequences are important for Som1p-dependent signal peptide cleavage in yeast mitochondria. J Biol Chem 279(38):39396-400
5) Longen S, et al.  (2009) Systematic analysis of the twin cx(9)c protein family. J Mol Biol 393(2):356-68
6) Neupert W and Herrmann JM  (2007) Translocation of proteins into mitochondria. Annu Rev Biochem 76:723-49
7) Mokranjac D and Neupert W  (2009) Thirty years of protein translocation into mitochondria: unexpectedly complex and still puzzling. Biochim Biophys Acta 1793(1):33-41
8) Nunnari J, et al.  (1993) A mitochondrial protease with two catalytic subunits of nonoverlapping specificities. Science 262(5142):1997-2004
9) Chen X, et al.  (1999) Signal peptides having standard and nonstandard cleavage sites can be processed by Imp1p of the mitochondrial inner membrane protease. J Biol Chem 274(53):37750-4
10) Pratje E and Guiard B  (1986) One nuclear gene controls the removal of transient pre-sequences from two yeast proteins: one encoded by the nuclear the other by the mitochondrial genome. EMBO J 5(6):1313-7
11) Esser K, et al.  (2004) The mitochondrial IMP peptidase of yeast: functional analysis of domains and identification of Gut2 as a new natural substrate. Mol Genet Genomics 271(5):616-26