title: The typically mitochondrial DNA-encoded ATP6 subunit of the F1F0-ATPase is encoded by a nuclear gene in Chlamydomonas reinhardtii.
abstract: The atp6 gene, encoding the ATP6 subunit of F(1)F(0)-ATP synthase, has thus far been found only as an mtDNA-encoded gene. However, atp6 is absent from mtDNAs of some species, including that of Chlamydomonas reinhardtii. Analysis of C. reinhardtii expressed sequence tags revealed three overlapping sequences that encoded a protein with similarity to ATP6 proteins. PCR and 5'- and 3'-RACE were used to obtain the complete cDNA and genomic sequences of C. reinhardtii atp6. The atp6 gene exhibited characteristics of a nucleus-encoded gene: Southern hybridization signals consistent with nuclear localization, the presence of introns, and a codon usage and a polyadenylation signal typical of nuclear genes. The corresponding ATP6 protein was confirmed as a subunit of the mitochondrial F(1)F(0)-ATP synthase from C. reinhardtii by N-terminal sequencing. The predicted ATP6 polypeptide has a 107-amino acid cleavable mitochondrial targeting sequence. The mean hydrophobicity of the protein is decreased in those transmembrane regions that are predicted not to participate directly in proton translocation or in intersubunit contacts with the multimeric ring of c subunits. This is the first example of a mitochondrial protein with more than two transmembrane stretches, directly involved in proton translocation, that is nucleus-encoded.
authors.affiliation: Departamento de Genética Molecular, Instituto de Fisiologia Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-243, 04510 México D.F., Mexico.
authors.forename: Soledad
authors.initials: S
authors.lastname: Funes
authors.forename: Edgar
authors.initials: E
authors.lastname: Davidson
authors.forename: M Gonzalo
authors.initials: MG
authors.lastname: Claros
authors.forename: Robert
authors.initials: R
authors.lastname: van Lis
authors.forename: Xochitl
authors.initials: X
authors.lastname: Pérez-Martínez
authors.forename: Miriam
authors.initials: M
authors.lastname: Vázquez-Acevedo
authors.forename: Michael P
authors.initials: MP
authors.lastname: King
authors.forename: Diego
authors.initials: D
authors.lastname: González-Halphen
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D002467:Cell Nucleus / Q000235:genetics*; D016825:Chlamydomonas reinhardtii / Q000201:enzymology / Q000235:genetics*; D003001:Cloning, Molecular; D004272:DNA, Mitochondrial / Q000235:genetics*; D020224:Expressed Sequence Tags; D025261:Mitochondrial Proton-Translocating ATPases; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D006180:Proton-Translocating ATPases / Q000235:genetics*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D004272:DNA, Mitochondrial; D000251:Adenosine Triphosphatases; D025261:Mitochondrial Proton-Translocating ATPases; D006180:Proton-Translocating ATPases