SAM37/YMR060C Summary Help

Standard Name SAM37 1
Systematic Name YMR060C
Alias MAS37 2 , PET3027 2 , TOM37 3
Feature Type ORF, Verified
Description Component of the Sorting and Assembly Machinery (SAM) complex; the SAM (or TOB) complex is located in the mitochondrial outer membrane; binds precursors of beta-barrel proteins and facilitates their outer membrane insertion; contributes to SAM complex stability (4, 5 and see Summary Paragraph)
Name Description Sorting and Assembly Machinery 1
Chromosomal Location
ChrXIII:392515 to 391532 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
Gbrowse
Gene Ontology Annotations All SAM37 GO evidence and references
  View Computational GO annotations for SAM37
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
High-throughput
Regulators 3 genes
Resources
Classical genetics
conditional
null
Large-scale survey
null
Resources
229 total interaction(s) for 186 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 3
  • Affinity Capture-RNA: 2
  • Affinity Capture-Western: 11
  • Two-hybrid: 1

Genetic Interactions
  • Dosage Lethality: 1
  • Dosage Rescue: 10
  • Negative Genetic: 149
  • Phenotypic Suppression: 2
  • Positive Genetic: 21
  • Synthetic Growth Defect: 14
  • Synthetic Lethality: 11
  • Synthetic Rescue: 4

Resources
Expression Summary
histogram
Resources
Length (a.a.) 327
Molecular Weight (Da) 37,493
Isoelectric Point (pI) 7.32
Localization
Phosphorylation PhosphoGRID | PhosphoPep Database
Structure
Homologs
sequence information
ChrXIII:392515 to 391532 | ORF Map | GBrowse
Note: this feature is encoded on the Crick strand.
SGD ORF map
Last Update Coordinates: 2011-02-03 | Sequence: 1996-07-31
Subfeature details
Relative
Coordinates
Chromosomal
Coordinates
Most Recent Updates
Coordinates Sequence
CDS 1..984 392515..391532 2011-02-03 1996-07-31
Retrieve sequences
Analyze Sequence
S288C only
S288C vs. other species
S288C vs. other strains
Resources
External Links All Associated Seq | Entrez Gene | Entrez RefSeq Protein | MIPS | Search all NCBI (Entrez) | UniProtKB
Primary SGDIDS000004664
SUMMARY PARAGRAPH for SAM37

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 SAM complex

The sorting and assembly machinery (SAM) complex, also known as the translocase of outer membrane beta-barrel proteins (TOB), is required for the correct insertion of beta-barrel proteins into the mitochondrial outer membrane (8). The core of this complex, which is located in the outer membrane, is composed of Sam50p/Tob55p, itself a beta-barrel protein; Sam37p/Mas37p; and Sam35p/Tob38p (9, 4, 10, 11, 12). Mdm10p, a protein first discovered for its role in mitochondrial morphology, also associates with the SAM complex (13).

Beta-barrel proteins are first translocated across the outer membrane by the translocase of the outer mitochondrial membrane (TOM) complex. After transit through the TOM complex into the intermembrane space, both of the complexes of small TIM proteins that reside there (Tim8p-Tim13p complex and Tim9p-Tim10p) are involved in delivery of the beta-barrel proteins to the SAM complex (14). The SAM complex then mediates insertion of the proteins into the mitochondrial outer membrane (15). The final steps of the process require Mdm10p as well as two other proteins implicated in maintenance of mitochondrial morphology, Mdm12p and Mmm1p, which themselves form a complex with Mdm10p (13). In addition to Sam50p/Tob55p, the beta-barrel proteins imported by this route include porin (Por1p or VDAC), the most abundant outer membrane protein; Mdm10p; and Tom40p, which comprises the pore of the TOM complex. All of these substrate proteins have a SAM complex recognition motif termed the beta-signal (15). The SAM complex is also required for correct insertion of some other subunits of the TOM complex, which do not have a beta-barrel structure, into the outer membrane: the entire complex is required for assembly of Tom22p into the TOM complex, while Sam37p only is required for assembly of Tom5p, Tom6p, and Tom7p (16).

about SAM37

Sam37p is exposed to the cytosolic face of the outer membrane (2, 4). It is not an essential component of the SAM complex but does contribute to its function, since the sam37 null mutant displays reduced import of beta-barrel proteins (4, 17, 11). Sam37p is not strongly conserved beyond the fungi (2). Its major function seems to be maintenance of the stability of the SAM complex, and it may also affect release of proteins from the complex (17).

Last updated: 2009-03-17 Contact SGD

References cited on this page View Complete Literature Guide for SAM37
1) Pfanner N, et al.  (2004) Assembling the mitochondrial outer membrane. Nat Struct Mol Biol 11(11):1044-8
2) Gratzer S, et al.  (1995) Mas37p, a novel receptor subunit for protein import into mitochondria. J Cell Biol 129(1):25-34
3) Pfanner N, et al.  (1996) Uniform nomenclature for the protein transport machinery of the mitochondrial membranes. Trends Biochem Sci 21(2):51-2
4) Wiedemann N, et al.  (2003) Machinery for protein sorting and assembly in the mitochondrial outer membrane. Nature 424(6948):565-71
5) Meisinger C, et al.  (2004) The mitochondrial morphology protein Mdm10 functions in assembly of the preprotein translocase of the outer membrane. Dev Cell 7(1):61-71
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) Paschen SA, et al.  (2005) Biogenesis of beta-barrel membrane proteins of mitochondria. Trends Biochem Sci 30(10):575-82
9) Kozjak V, et al.  (2003) An essential role of Sam50 in the protein sorting and assembly machinery of the mitochondrial outer membrane. J Biol Chem 278(49):48520-3
10) Milenkovic D, et al.  (2004) Sam35 of the mitochondrial protein sorting and assembly machinery is a peripheral outer membrane protein essential for cell viability. J Biol Chem 279(21):22781-5
11) Waizenegger T, et al.  (2004) Tob38, a novel essential component in the biogenesis of beta-barrel proteins of mitochondria. EMBO Rep 5(7):704-9
12) Ishikawa D, et al.  (2004) Two novel proteins in the mitochondrial outer membrane mediate beta-barrel protein assembly. J Cell Biol 166(5):621-7
13) Meisinger C, et al.  (2007) The morphology proteins Mdm12/Mmm1 function in the major beta-barrel assembly pathway of mitochondria. EMBO J 26(9):2229-39
14) Wiedemann N, et al.  (2004) Biogenesis of the protein import channel Tom40 of the mitochondrial outer membrane: intermembrane space components are involved in an early stage of the assembly pathway. J Biol Chem 279(18):18188-94
15) Kutik S, et al.  (2008) Dissecting membrane insertion of mitochondrial beta-barrel proteins. Cell 132(6):1011-24
16) Stojanovski D, et al.  (2007) Alternative function for the mitochondrial SAM complex in biogenesis of alpha-helical TOM proteins. J Cell Biol 179(5):881-93
17) Chan NC and Lithgow T  (2008) The peripheral membrane subunits of the SAM complex function codependently in mitochondrial outer membrane biogenesis. Mol Biol Cell 19(1):126-36