Isolation and characterization of a human cDNA encoding a protein homologous to the 7.2-kDa protein (subunit X) of bovine ubiquinol-cytochrome C reductase

Through large-scale sequencing of clones randomly selected from a library o f human cDNAs, we have isolated a novel human gene termed hUQCR10. Its open reading frame encodes 63 amino acids that share 88.5% identity with the se quence of bovine ubiquinol-cytochrome C reductase 7.2-kDa protein (subunit X). A single 0.6-kb transcript was expressed in all human tissues examined, but was particularly abundant in heart and skeletal muscle, tissues that c onsume a large amount of oxygen. The gene product therefore may play a sign ificant role in the cellular respiratory system. In support of this hypothe sis, our immunohistochemical analysis revealed that the hUQCR10 protein is located in mitochondria. A homology search using computer programs determin ed the chromosomal localization of the gene at 22q12.