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Tom20 recognizes mitochondrial presequences through dynamic equilibrium among multiple bound states.


ABSTRACT: Most mitochondrial proteins are synthesized in the cytosol and imported into mitochondria. The N-terminal presequences of mitochondrial-precursor proteins contain a diverse consensus motif (phi chi chi phi phi, phi is hydrophobic and chi is any amino acid), which is recognized by the Tom20 protein on the mitochondrial surface. To reveal the structural basis of the broad selectivity of Tom20, the Tom20-presequence complex was crystallized. Tethering a presequence peptide to Tom20 through a disulfide bond was essential for crystallization. Unexpectedly, the two crystals with different linker designs provided unique relative orientations of the presequence with respect to Tom20, and neither configuration could fully account for the hydrophobic preference at the three hydrophobic positions of the consensus motif. We propose the existence of a dynamic equilibrium in solution among multiple states including the two bound states. In accordance, NMR 15N relaxation analyses suggested motion on a sub-millisecond timescale at the Tom20-presequence interface. We suggest that the dynamic, multiple-mode interaction is the molecular mechanism facilitating the broadly selective specificity of the Tom20 receptor toward diverse mitochondrial presequences.

SUBMITTER: Saitoh T 

PROVIDER: S-EPMC2080804 | biostudies-literature | 2007 Nov

REPOSITORIES: biostudies-literature

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Tom20 recognizes mitochondrial presequences through dynamic equilibrium among multiple bound states.

Saitoh Takashi T   Igura Mayumi M   Obita Takayuki T   Ose Toyoyuki T   Kojima Rieko R   Maenaka Katsumi K   Endo Toshiya T   Kohda Daisuke D  

The EMBO journal 20071018 22


Most mitochondrial proteins are synthesized in the cytosol and imported into mitochondria. The N-terminal presequences of mitochondrial-precursor proteins contain a diverse consensus motif (phi chi chi phi phi, phi is hydrophobic and chi is any amino acid), which is recognized by the Tom20 protein on the mitochondrial surface. To reveal the structural basis of the broad selectivity of Tom20, the Tom20-presequence complex was crystallized. Tethering a presequence peptide to Tom20 through a disulf  ...[more]

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