Topological analysis of the peripheral benzodiazepine receptor in yeast mitochondrial membranes supports a five-transmembrane structure.
The peripheral benzodiazepine receptor, implicated in the transport of cholesterol from the outer to the inner mitochondrial membrane, is predicted by hydropathy analysis to feature five membrane-spanning domains, with the amino terminus within the mitochondrial periplasm and the carboxyl terminus in the external cytoplasm. We have tested these structural predictions directly by immunodetection of c-Myc-tagged peripheral benzodiazepine receptor on intact yeast mitochondria and by specific labeling in yeast membranes of cysteine residues introduced by site-directed mutagenesis. The combined results support the model originally proposed with some minor but important modifications. The theoretical model predicted relatively short alpha-helical domains, only long enough to span a phospholipid monolayer, whereas the results presented here would support a model with extended alpha-helices sufficiently long to span an entire membrane bilayer, with concomitant shorter loop and tail regions.
Joseph-Liauzun
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Department of Microbiology, Sanofi Recherche, Centre de Labège, France. evelyne.liauzun@tls1.elfsanofi.fr
Delmas
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Shire
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Ferrara
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D000595:Amino Acid Sequence; D001692:Biological Transport; D002784:Cholesterol / Q000378:metabolism; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000032:analysis; D004797:Enzyme-Linked Immunosorbent Assay; D018604:Epitope Mapping; D007425:Intracellular Membranes / Q000737:chemistry*; D008928:Mitochondria / Q000737:chemistry*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D016271:Proto-Oncogene Proteins c-myc / Q000737:chemistry; D011963:Receptors, GABA-A / Q000737:chemistry* / Q000235:genetics; D012441:Saccharomyces cerevisiae
D016271:Proto-Oncogene Proteins c-myc; D011963:Receptors, GABA-A; D002784:Cholesterol; D003545:Cysteine