Disease relevance of TOMM20

• Phage display was used to identify new components of the mammalian mitochondrial receptor complex using Tom20 as a binding partner [1].

High impact information on TOMM20

• Insertion of PorB into the mitochondrial outer membrane in vitro depends on the activity of Tom5, Tom20 and Tom40, but is independent of Tom70 [2].
• Tom22 forms a complex with Tom20, and its cytosolic domain functions as an import receptor as in fungi [3].
• In vitro binding assays showed that Tom20 binds to guanidinium chloride unfolded substrate proteins regardless of the presence or absence of presequences [4].
• This activity was inhibited by a presequence peptide, suggesting that the binding site of Tom20 for presequence is identical or close to the active site for the chaperone-like activity [4].
• We constructed a structural model for the interaction between the amino-terminal end of PPOX and the putative mitochondrial receptor protein Tom20 [5].

Biological context of TOMM20

• Gene structure of the human mitochondrial outer membrane receptor Tom20 and evolutionary study of its family of processed pseudogenes [6].
• Renal expression of sodium-potassium adenosinetriphosphatase (Na(+)-K(+)-ATPase) and two reflectors of mitochondrial biogenesis [mitochondrial transcription factor A (TFAM) and translocase of outer mitochondrial membrane 20 (TOM20)] also were studied using Western immunoblotting and immunohistochemistry [7].
• Tom20, a mitochondrial outer membrane receptor necessary for protein translocation, was found to interact specifically with mitochondrial preproteins [8].
• Thus Tom20 is important in determining import during organelle biogenesis, but other mechanisms (e.g., intramitochondrial protein degradation or nuclear transcription) likely also play a role in establishing the final mitochondrial phenotype during normal muscle differentiation [9].
• These data indicate a close relationship between induced changes in Tom20 and the import of a matrix protein, suggesting that Tom20 is involved in determining the kinetics of import [9].

Anatomical context of TOMM20

• Rather, two major components from the TOM (translocase of the outer mitochondrial membrane) complex, namely TOM20 and TOM40, are important for tRNA binding at the surface of mitochondria, suggesting that they are also involved in tRNA import [10].
• Functional analysis of human mitochondrial receptor Tom20 for protein import into mitochondria [11].
• Requirement of the mitochondrial import receptor Tom20 in protein import into mammalian mitochondria was studied in vitro and in cultured cells [12].
• However, the mammalian protein exhibits only weak homology to the tetratricopeptide repeat B domain that is found in Mas20p/MOM19. huMas20p is targeted and inserted into the outer membrane of isolated rat heart mitochondria, in the Nin-Ccyto orientation [13].
• In the final step the plasma membrane-derived microsome fraction proved to be devoid of contamination by outer mitochondrial membranes, as revealed by antibodies against the established markers MAO B and Tom20 applied in Western blots [14].

Associations of TOMM20 with chemical compounds

• Human mitochondrial import receptor, Tom20p. Use of glutathione to reveal specific interactions between Tom20-glutathione S-transferase and mitochondrial precursor proteins [15].
• Antibodies against Tom20 coprecipitated both the precursor of aldehyde dehydrogenase (pALDH) and of dihydrofolate reductase (pA-DHFR) [16].
• Previous studies pointed to the importance of leucine residues in the binding of mitochondrial leader sequences to Tom20, an outer membrane protein translocator that initially binds the leader during import [17].
• Using Western blot analysis, the ratio of Tom20 (normalized to Ponceau S) between mitochondria isolated from the anterior ischemic and posterior control wall was reduced (0.72 +/- 0.11, a.u., n = 8), whereas the mitochondrial Tom20 content was preserved by IP (1.17 +/- 0.16 a.u., n = 7, P < 0.05) [18].
• We found that interactions of Bcl-2alpha with the mitochondrial import receptor Tom20 are dependent on two positively charged lysine residues in the immediate vicinity of the carboxy-terminal hydrophobic membrane anchor [19].

Regulatory relationships of TOMM20

• Only Tom20 inhibited the import of a fusion protein of the leader of aldehyde dehydrogenase attached to dihydrofolate reductase [16].

Other interactions of TOMM20

• A cell-free immunoprecipitation assay indicated that an internal segment of the Tom22 cytosolic domain is important for interaction with Tom20 [3].
• Tom34 unlike Tom20 does not interact with the leader sequences of mitochondrial precursor proteins [16].
• The mitochondrial import receptor translocase of the outer membrane of mitochondria (Tom20) consists of five segments, an N-terminal membrane-anchor segment, a linker segment rich in charged amino acids, a tetratricopeptide repeat motif, a glutamine-rich segment, and a C-terminal segment [11].
• Coexpression of metaxin with Tom20 had no further effect on the preprotein import [20].
• Renal expression of TFAM and TOM20 was not altered by neonatal enalapril treatment [7].

Analytical, diagnostic and therapeutic context of TOMM20

• Prevention of the ischemia-induced decrease in mitochondrial Tom20 content by ischemic preconditioning [18].
• Interaction between mitochondrial precursor proteins and cytosolic soluble domains of mitochondrial import receptors, Tom20 and Tom70, measured by surface plasmon resonance [21].
• A yeast two-hybrid assay revealed that the import sequence interacted with two intramolecular elements, the TMD and C-tail signal, and that it also interacted with the import receptor Tom20 [22].
• The 23-kDa protein is identical to the previously characterized potato TOM20 receptor, as shown by in vitro assembly of this protein into the 230-kDa complex, by immunoblotting and by direct protein sequencing [23].
• In vitro functional assays and peptide titrations suggest that the plant Tom20 is functionally equivalent to fungal and animal Tom20s [24].

References