Roles of Tom70 in import of presequence-containing mitochondrial proteins.
Mitochondrial protein traffic requires precise recognition of the mitochondrial targeting signals by the import receptors on the mitochondrial surface including a general import receptor Tom20 and a receptor for presequence-less proteins, Tom70. Here we took a proteome-wide approach of mitochondrial protein import in vitro to find a set of presequence-containing precursor proteins for recognition by Tom70. The presequences of the Tom70-dependent precursor proteins were recognized by Tom20, whereas their mature parts exhibited Tom70-dependent import when attached to the presequence of Tom70-independent precursor proteins. The mature parts of the Tom70-dependent precursor proteins have the propensity to aggregate, and the presence of the receptor domain of Tom70 prevents their aggregate formation. Therefore Tom70 plays the role of a docking site for not only cytosolic chaperones but also aggregate-prone substrates to maintain their solubility for efficient transfer to downstream components of the mitochondrial import machineries.
Yamamoto
Hayashi
H
Department of Chemistry, Graduate School of Science, Japan Science and Technology Agency, Research Centre for Material Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan.
Fukui
Kenji
K
Takahashi
Hisashi
H
Kitamura
Shingo
S
Shiota
Takuya
T
Terao
Kayoko
K
Uchida
Mayumi
M
Esaki
Masatoshi
M
Nishikawa
Shuh-ichi
S
Yoshihisa
Tohru
T
Yamano
Koji
K
Endo
Toshiya
T
D015180:Electrophoresis, Gel, Two-Dimensional; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D018832:Molecular Chaperones; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism*; D020543:Proteome / Q000032:analysis*; D012331:RNA, Fungal / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D033681:Mitochondrial Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins; D018832:Molecular Chaperones; D011498:Protein Precursors; D020543:Proteome; D012331:RNA, Fungal; D029701:Saccharomyces cerevisiae Proteins; C489039:TOM70 protein, S cerevisiae