title: The Oxa1 protein forms a homooligomeric complex and is an essential part of the mitochondrial export translocase in Neurospora crassa.
abstract: The Oxa1 protein is a ubiquitous constituent of the inner membrane of mitochondria. Oxa1 was identified in yeast as a crucial component of the protein export machinery known as the OXA translocase, which facilitates the integration of proteins from the mitochondrial matrix into the inner membrane. We have identified the Neurospora crassa Oxa1 protein which shows a sequence identity of 22% to the yeast homologue. Despite the low level of identity, the function of the homologues is conserved as the N. crassa gene fully complemented a yeast null mutant. Genetic analysis revealed that Oxa1 is essential for viability in N. crassa. Cells propagated under conditions that severely reduce Oxa1 levels grew extremely slowly and were deficient in subunits of complex I and complex IV. Isolation of the Oxa1 complex from N. crassa mitochondria revealed a 170-180-kDa complex that contained exclusively Oxa1. Since the Oxa1 monomer has a molecular weight of 43,000, our data suggest that the OXA translocase consists of a homooligomer most likely containing four Oxa1 subunits.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada. frank.nargang@ualberta.ca
authors.forename: Frank E
authors.initials: FE
authors.lastname: Nargang
authors.forename: Marc
authors.initials: M
authors.lastname: Preuss
authors.forename: Walter
authors.initials: W
authors.lastname: Neupert
authors.forename: Johannes M
authors.initials: JM
authors.lastname: Herrmann
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001704:Biopolymers / Q000378:metabolism*; D017931:DNA Primers; D003902:Detergents; D003576:Electron Transport Complex IV; D005816:Genetic Complementation Test; D008928:Mitochondria / Q000201:enzymology*; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D009492:Neurospora crassa / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D001704:Biopolymers; D017931:DNA Primers; D003902:Detergents; D024101:Mitochondrial Proteins; D009687:Nuclear Proteins; C090858:OXA1 protein; D003576:Electron Transport Complex IV