Selectivity changes in site-directed mutants of the VDAC ion channel: structural implications.
The gene encoding the yeast mitochondrial outer membrane channel VDAC was subjected to site-directed mutagenesis to change amino acids at 29 positions to residues differing in charge from the wild-type sequence. The mutant genes were then expressed in yeast, and the physiological consequences of single and multiple amino acid changes were assessed after isolation and insertion of mutant channels into phospholipid bilayers. Selectivity changes were observed at 14 sites distributed throughout the length of the molecule. These sites are likely to define the position of the protein walls lining the aqueous pore and hence, the transmembrane segments. These results have been used to develop a model of the open state of the channel in which each polypeptide contributes 12 beta strands and one alpha helix to form the aqueous transmembrane pathway.
Vollum Institute for Advanced Biomedical Research, Oregon Health Sciences University, Portland 97201.
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Blachly-Dyson
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S
Peng
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Colombini
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M
Forte
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D007425:Intracellular Membranes / Q000502:physiology; D007473:Ion Channels; D008051:Lipid Bilayers / Q000378:metabolism; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000235:genetics* / Q000502:physiology; D008928:Mitochondria / Q000648:ultrastructure; D008969:Molecular Sequence Data; D009154:Mutation; D018272:Porins; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000648:ultrastructure; D013329:Structure-Activity Relationship; D050994:Voltage-Dependent Anion Channels
D007473:Ion Channels; D008051:Lipid Bilayers; D008565:Membrane Proteins; D018272:Porins; D050994:Voltage-Dependent Anion Channels