Construction of a cDNA clone for a nuclear-coded subunit of cytochrome c oxidase from rat liver

A cDNA library for 6S-9S poly(A)-containing RNA from rat liver was constructed in E. coli. Initial screening of the clones was carried out using single stranded 32P-labeled cDNA prepared against poly(A)-containing RNA isolated from immunoadsorbed polyribosomes enriched for the nuclear-coded subunit messenger RNAs of cytochrome c oxidase. One of the clones, pCO89, was found to hybridize with the messenger RNA for subunit VIC. The DNA sequence of the insert in pCO89 was carried out and it has got extensive homology with the C-terminal 33 amino acids of subunit VIC from beef heart cytochrome c oxidase. In addition, the insert contained 146 bp, corresponding to a portion of the 3'-non-coding region. Northern blot analysis of rat liver RNA with the nick-translated insert of pCO89 revealed that the messenger RNA for subunit VI would contain around 510 bases.