The 9.8 kDa subunit of complex I, related to bacterial Na(+)-translocating NADH dehydrogenases, is required for enzyme assembly and function in Neurospora crassa.
A nuclear gene encoding a 9.8 kDa subunit of complex I, the homologue of mammalian MWFE protein, was identified in the genome of Neurospora crassa. The gene was cloned and inactivated in vivo by the generation of repeat-induced point mutations. Fungal mutant strains lacking the 9.8 kDa polypeptide were subsequently isolated. Analyses of mitochondrial proteins from mutant nuo9.8 indicate that the membrane and peripheral arms of complex I fail to assemble. Respiration of mutant mitochondria on matrix NADH is rotenone-insensitive, confirming that the 9.8 kDa protein is required for the assembly and activity of complex I. We found a similarity between the MWFE homologues and the C-terminal part of the nqrA subunit of bacterial Na(+)-translocating NADH:quinone oxidoreductases (Na(+)-NQR), suggesting a link between proton-pumping and sodium-pumping NADH dehydrogenases.
Marques
Isabel
I
Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.
Duarte
Margarida
M
Videira
Arnaldo
A
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000235:genetics; D003001:Cloning, Molecular; D017931:DNA Primers / Q000737:chemistry; D005656:Fungal Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D007114:Immunization; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009492:Neurospora crassa / Q000201:enzymology* / Q000235:genetics; D010101:Oxygen Consumption; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D011808:Quinone Reductases / Q000235:genetics / Q000378:metabolism*; D011817:Rabbits; D012402:Rotenone / Q000494:pharmacology; D017386:Sequence Homology, Amino Acid; D012964:Sodium / Q000378:metabolism*
D017931:DNA Primers; D005656:Fungal Proteins; D008565:Membrane Proteins; C492251:Ndufa1 protein, mammalian; D012402:Rotenone; D012964:Sodium; C041831:NADH dehydrogenase (quinone); D011808:Quinone Reductases