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Mitochondrial ATP synthase subunit 9 is not required for viability of the petite-negative yeast Kluyveromyces lactis

Clark-Walker, G.D., Francois, F., Chen, X.J., Vieira Da Silva, M.R., Claisse, M.L.
Current genetics 1997 v.31 no.6 pp. 488-493
Kluyveromyces marxianus var. lactis, pyrophosphatases, mitochondrial DNA, introns, structural genes, ribosomal DNA, mutants, viability, nucleotide sequences, amino acid sequences, genetic recombination, phenotype, repetitive sequences
Specific mutations in nuclear MGI genes encoding the or, alpha and beta and gamma subunits of the mitochondrial inner membrane F1-ATPase complex allow mitochondrial DNA (mtDNA) to be lost from K. lactis. In the absence of a mutation in any of these three nuclear genes, loss of mtDNA is lethal. These results imply that mtDNA encodes a gene that is essential. Likely candidates for such an essential role are the ATP6, 8 and 9 genes coding for proteins of the ATP synthase-F0 component. The present study removes ATP9 from contention as a vital mitochondrial gene because in a respiratory deficient mutant, Gly- 3.9, lacking a nuclear mgi mutation, we have found that a rearrangement in mtDNA has deleted 22 amino acids from the carboxy terminus of the 75 amino-acid subunit-9 protein. Rearrangement in mtDNA has occurred by recombination that a 23-bp repeated sequence in the introns of the ATP9 and large ribosomal RNA (LSU) subunit genes. These two introns, of 394 (ATP9) and 410 (LSU) nucleotides, both belong to group 1.