High impact information on TOM20

• We report here the NMR structure of a general import receptor, rat Tom20, in a complex with a presequence peptide derived from rat aldehyde dehydrogenase [1].
• The single membrane anchor of Tom22 is required for a stable interaction between the core complexes, whereas its cytosolic domain serves as docking point for the peripheral receptors Tom20 and Tom70 [2].
• Targeting of the master receptor MOM19 to mitochondria [3].
• The deduced amino acid sequence predicts that MOM19 is anchored in the outer membrane by an NH2-terminal hydrophobic sequence, while the rest of the protein forms a hydrophilic domain exposed to the cytosol [3].
• We have isolated the TOM core complex of Neurospora crassa by removing the receptors Tom70 and Tom20 from the isolated TOM holo complex by treatment with the detergent dodecyl maltoside [4].

Biological context of TOM20

• Overexpression of Mom22 even suppressed the lethal phenotype of a double deletion of the two import receptors known so far (mom19 delta mom72 delta) [5].
• Import of the purified precursor showed the characteristics of authentic mitochondrial import including use of the receptor MOM19, requirement for a membrane potential, and proteolytic processing [6].
• Hidden Markov model searches of genome sequence data revealed novel isoforms of Tom20 in vertebrate and invertebrate animals [7].
• Transmembrane translocation of the tRNA requires the intactness of at least two of the components of the mitochondrial import machinery of pre-proteins, MOM19 and MIM44, as well as energy of ATP hydrolysis and an electrochemical potential across the inner membrane [8].

Anatomical context of TOM20

• Import of porin into isolated mitochondria in which the outer membrane has been opened is inhibited despite similar levels of Tom20 as in intact mitochondria [9].
• Mas20p and Mas70p are integral proteins of the yeast mitochondrial outer membrane that appear to function as receptors for precursor proteins imported from the cytosol [10].
• Tom20 is an outer mitochondrial membrane protein and functions as a component of the import receptor complex for the cytoplasmically synthesized mitochondrial precursor proteins [11].

Physical interactions of TOM20

• The Mas20p and Mas70p subunits of the protein import receptor of yeast mitochondria interact via the tetratricopeptide repeat motif in Mas20p: evidence for a single hetero-oligomeric receptor [12].

Other interactions of TOM20

• (ii) Tom20 and Tom70 are not essential for the generation of the GIP complex [13].
• It was unknown if Mom22 directly interacts with preproteins, and two views existed about the possible functions of Mom22: a central role in transfer of preproteins from both receptors to the general insertion pore or a more limited function dependent on the presence of the receptor Mom19 [5].
• Preproteins carrying amino-terminal signals mainly use Tom20, the general import pore (GIP) complex and the Tim23-Tim17 complex [14].
• We report that import of the preprotein of Tim22 requires Tom20, although it uses the carrier Tim route [14].
• Surprisingly, AAC is still associated with the receptors Tom70 and Tom20 when the function of Tim10 is impaired [15].

References