title: URF13, a maize mitochondrial pore-forming protein, is oligomeric and has a mixed orientation in Escherichia coli plasma membranes.
abstract: URF13, an inner mitochondrial membrane protein of the maize Texas male-sterile cytoplasm (cms-T), has one orientation in the inner membrane of maize mitochondria but two topological orientations in the plasma membrane when expressed in Escherichia coli. Antibodies specific for the carboxyl terminus of URF13 and for an amino-terminal tag fused to URF13 in E. coli were used to determine the location of each end of the protein following protease treatments of right-side-out and inside-out vesicles derived from cms-T mitochondria and the E. coli plasma membrane. Cross-linking studies indicate that a portion of the URF13 population in mitochondria and E. coli exists in membranes in an oligomeric state and, in combination with proteolysis studies, show that individual subunits within a given multimer have the same orientation. A three-membrane-spanning helical model for URF13 topology is presented.
authors.affiliation: Department of Genetics, North Carolina State University, Raleigh 27695-7614.
authors.forename: K L
authors.initials: KL
authors.lastname: Korth
authors.forename: C I
authors.initials: CI
authors.lastname: Kaspi
authors.forename: J N
authors.initials: JN
authors.lastname: Siedow
authors.forename: C S
authors.initials: CS
authors.lastname: Levings
mesh_terms: D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D003001:Cloning, Molecular; D003432:Cross-Linking Reagents / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D015151:Immunoblotting; D007425:Intracellular Membranes / Q000378:metabolism / Q000648:ultrastructure; D046911:Macromolecular Substances; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D024101:Mitochondrial Proteins; D008961:Models, Structural; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D010957:Plasmids; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D003313:Zea mays / Q000235:genetics / Q000378:metabolism*
chemical_list: D003432:Cross-Linking Reagents; D046911:Macromolecular Substances; D024101:Mitochondrial Proteins; D010940:Plant Proteins; D011994:Recombinant Proteins; C071393:URF13 protein, Zea mays