Biochemistry and Pharmacology - Research Publications

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Subject: Biochemistry and Cell Biology not elsewhere classified ; Biological Sciences × Author: Perugini, Matthew × Author: LITHGOW, TREVOR ×

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    A biophysical analysis of the tetratricopeptide repeat-rich mitochondrial import receptor, Tom70, reveals an elongated monomer that is inherently flexible, unstable, and unfolds via a multistate pathway
    Beddoe, T ; Bushell, SR ; Perugini, MA ; Lithgow, T ; Mulhern, TD ; Bottomley, SP ; Rossjohn, J (AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC, 2004-11-05)
    Proteins destined for all submitochondrial compartments are translocated across the outer mitochondrial membrane by the TOM (translocase of the outer membrane) complex, which consists of a number of specialized receptor subunits that bind mitochondrial precursor proteins for delivery into the translocation channel. One receptor, Tom70, binds large, hydrophobic mitochondrial precursors. The current model of Tom70-mediated import involves multiple dimers of the receptor recognizing a single molecule of substrate. Here we show via a battery of biophysical and spectroscopic techniques that the cytosolic domain of Tom70 is an elongated monomer. Thermal and urea-induced denaturation revealed that the receptor, which unfolds via a multistate pathway, is a relatively unstable molecule undergoing major conformational change at physiological temperatures. The data suggest that the malleability of the monomeric Tom70 receptor is an important factor in mitochondrial import.