Isolation of a single nuclear gene encoding human ubiquinone-binding protein in complex III of mitochondrial respiratory chain.

We have isolated five genomic DNA clones which contain nucleotide sequences hybridizable to a cDNA for human ubiquinone-binding protein in Complex III (QP). Nucleotide sequence analysis revealed that two of them contained different types of pseudogenes suggesting molecular evolution of the gene, and that the other three clones contained the overlapping fragments from the same QP gene. The gene spans 4.5 to 5 kb in length. The sequences of exons in the gene were determined and found to be identical to the corresponding parts of the human QP cDNA. The exon-intron boundaries follow the GT/AG rule. Two CAAT boxes were found in the promoter region. It is concluded from these results that the isolated human QP gene is functional. Genomic Southern blot analysis showed that the gene is present in a single copy in the human genome.