The C-terminal TPR Domain of Tom70 Defines a Family of Mitochondrial Protein Import Receptors Found only in Animals and Fungi

Roles of Tom70 in Import of Presequence-containing Mitochondrial Proteins

“…Now the present study indicated that although Tom70 can recognize substrates with internal targeting signals as their cognate receptor, it also receives some substrates as a chaperone even if they do not have internal signals. This is in good accordance with the previous bioinformatics-based proposal that hydrophobic mitochondrial proteins, irrespective of the presence of presequences, could be substrates for Tom70 (17). Perhaps a cytosolic chaperone and its substrate may still form a complex on Tom70 for a while.…”

“…Therefore aggregate-prone mitochondrial precursor proteins require cytosolic chaperones including yeast Hsp70 (17,27,28) to maintain their solubility or import competence. Tom70 is known to function as a docking site for those chaperones to recruit the chaperone-substrate complexes to the TOM40 complex (19).…”

“…It has been reported that Tom70 recognizes, in addition to presequenceless polytopic membrane proteins, some presequence-containing precursor proteins including cytochrome c 1 , alcohol dehydrogenase III, and the ␣-and ␤-subunits of F 1 -ATPase (Atp1p and Atp2p); yet the presequences did not appear to be the sole determinant of those presequence-containing precursors to Tom70 (14 -16). The purified presequence-containing adrenodoxin precursor loaded onto the cytosolic chaperone mitochondrial import-stimulating factor was shown to bind to Tom70 first and then to Tom20 during its import into mitochondria in vitro (17). However, in contrast to Tom20, little is known about the recognition of the mitochondrial targeting signal by Tom70, although a peptide scan analysis showed that Tom70 binds to multiple segments throughout the polypeptide chain of noncleavable phosphate carrier (18).…”

An Internal EELD Domain Facilitates Mitochondrial Targeting of Mcl-1 via a Tom70-dependent Pathway

“…In contrast, the Tom70 mutant study seems to be inconsistent with that obtained by the yeast-two hybrid screen where Tom70 clones without the N-terminal clamp domain were fished out by Mcl-1. Our best interpretation for these inconsistent results is that other structurally similar TPR motifs present in the core and/or the C-terminal region of Tom70 (Chan et al, 2006;Wu and Sha, 2006) may have mediated the Tom70 -Mcl-1 interaction in the yeast twohybrid assay, whose sensitivity apparently differs from that of the co-IP or the GST pull-down assays. The DM Mutant Is Significantly Less Targeted to Mitochondria Next, we examined whether the L126A and D127A mutations affect the subcellular localization of Mcl-1.…”

Caracterização do papel da glutamil-tRNA sintetase na localização subcelular de proteínas

“…Nas plantas este complexo compreende sete proteínas (MACASEV et al, 2000;MACASEV et al, 2004;CHAN et al, 2006;CHEW et al, 2004 ). O complexo Sam compreende três proteínas integrais, que atuam na montagem de proteínas do complexo Tom (CHACINSKA et al, 2010).…”