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Endoplasmic-reticulum membrane; Protein import receptor; General insertion pore; Precursor proteins; Escherichia-coli; Neurospora-crassa; Secretory proteins; Cationic channel; Cell viability; Complex.; Cell & developmental biology.
Abstract:
The preprotein translocase of the outer membrane of mitochondria (TOM complex) facilitates the recognition, insertion, and translocation of nuclear-encoded mitochondrial preproteins. We have purified the TOM complex from Neurospora crassa and analyzed its composition and functional properties. The TOM complex contains a cation-selective high-conductance channel. Upon reconstitution into liposomes, it mediates integration of proteins into and translocation across the lipid bilayer. TOM complex particles have a diameter of about 138 Angstrom, as revealed by electron microscopy and image analysis; they contain two or three centers of stain-filled openings, which we interpret as pores with an apparent diameter of about 20 Angstrom. We conclude that the structure reported here represents the protein-conducting channel of the mitochondrial outer membrane. [References: 75]
