Binding of a synthetic targeting peptide to a mitochondrial channel protein.
Membrane crystals of the mitochondrial outer membrane channel VDAC (porin) from Neurospora crassa were incubated with a 20-amino-acid synthetic peptide corresponding to the N-terminal targeting region of subunit IV of cytochrome oxidase. The peptide caused disordering and contraction of the crystal lattice of the membrane arrays. Also, new stain-excluding features were observed on the peptide-treated arrays which most likely correspond to sites at which the peptide accumulates. The stain exclusion zones associated with binding of the targeting peptide (and with binding of apocytochrome c in an earlier study) have been localized on a two-dimensional density map of frozen-hydrated, crystalline VDAC previously obtained by cryo-electron microscopy. The results indicate that both the peptide and cytochrome c bind to protein "arms" which extend laterally between the channel lumens. The finding that imported polypeptides bind to a specific region of the VDAC protein implicates this channel in the process by which precursor proteins are recognized at and translocated across the mitochondrial outer membrane.
Mannella
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CA
Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany 12201-0509.
Guo
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XW
Dias
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J
D000595:Amino Acid Sequence; D001665:Binding Sites; D003460:Crystallization; D003576:Electron Transport Complex IV / Q000138:chemical synthesis / Q000378:metabolism*; D007091:Image Processing, Computer-Assisted; D007473:Ion Channels / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism* / Q000648:ultrastructure; D008854:Microscopy, Electron; D008928:Mitochondria / Q000378:metabolism*; D008969:Molecular Sequence Data; D009491:Neurospora; D010455:Peptides / Q000138:chemical synthesis / Q000378:metabolism; D018272:Porins; D011485:Protein Binding; D013194:Staining and Labeling; D050994:Voltage-Dependent Anion Channels
D007473:Ion Channels; D008565:Membrane Proteins; D010455:Peptides; D018272:Porins; D050994:Voltage-Dependent Anion Channels; D003576:Electron Transport Complex IV