Recognition of preproteins by the isolated TOM complex of mitochondria

AUTOR(ES)

Stan, Tincuta

FONTE

Oxford University Press

RESUMO

A multisubunit complex in the mitochondrial outer membrane, the TOM complex, mediates targeting and membrane translocation of nuclear-encoded preproteins. We have isolated the TOM holo complex, containing the preprotein receptor components Tom70 and Tom20, and the TOM core complex, which lacks these receptors. The interaction of recombinant mitochondrial preproteins with both types of soluble TOM complex was analyzed. Preproteins bound efficiently in a specific manner to the isolated complexes in the absence of chaperones and lipids in a bilayer structure. Using fluorescence correlation spectroscopy, a dissociation constant in the nanomolar range was determined. The affinity was lower when the preprotein was stabilized in its folded conformation. Following the initial binding, the presequence was transferred into the translocation pore in a step that required unfolding of the mature part of the preprotein. This translocation step was also mediated by protease-treated TOM holo complex, which contains almost exclusively Tom40. Thus, the TOM core complex, consisting of Tom40, Tom22, Tom6 and Tom7, is a molecular machine that can recognize and partially translocate mitochondrial precursor proteins.

Documentos Relacionados

• Dynamics of the TOM Complex of Mitochondria during Binding and Translocation of Preproteins
• Mitochondrial Protein Import: Recognition of Internal Import Signals of BCS1 by the TOM Complex
• Protein Import Channel of the Outer Mitochondrial Membrane: a Highly Stable Tom40-Tom22 Core Structure Differentially Interacts with Preproteins, Small Tom Proteins, and Import Receptors
• Reconstituted TOM Core Complex and Tim9/Tim10 Complex of Mitochondria Are Sufficient for Translocation of the ADP/ATP Carrier across Membranes
• Structural Requirements of Tom40 for Assembly into Preexisting TOM Complexes of Mitochondria