Roles of Tom70 in Import of Presequence-containing Mitochondrial Proteins |
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| Authors: | Hayashi Yamamoto Kenji Fukui Hisashi Takahashi Shingo Kitamura Takuya Shiota Kayoko Terao Mayumi Uchida Masatoshi Esaki Shuh-ichi Nishikawa Tohru Yoshihisa Koji Yamano and Toshiya Endo |
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| Institution: | From the ‡Department of Chemistry, Graduate School of Science, ;the §Research Centre for Material Science, and ;¶Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Research Centre for Material Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan |
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| Abstract: | 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. |
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