Expression of the human ADCK3 polypeptide partially restores Q6 content in yeast coq8 mutants. Yeast cells were cultured in YPGal + 0.1% dextrose and collected at an optical density (A600nm) of about 1.0. The content of Q6 in yeast cell lipid extracts was determined by HPLC/MS-MS as described in Experimental Procedures. Yeast coq8 mutants were transformed with plasmids expressing yeast ABC1/COQ8 (low-copy, p3HN4), human CABC1/ADCK3 (multi-copy, pmcADCK3), or empty vector control (multi-copy, pRS426). Each bar represents a total of four measurements from two independent samples each with two injections. Standard deviations are represented with error bars. Q4 was used as internal standard.