Isolation and characterization of the mitochondrial ATP synthase from Chlamydomonas reinhardtii. CDNA sequence and deduced protein sequence of the alpha subunit

We have isolated the F0F1-ATP synthase complex from oligomycin-sensitive mitochondria of the green alga Chlamydomonas reinhardtii. A pure and active ATP synthase was obtained by means of sonication, extraction with dodecyl maltoside and ion exchange and gel permeation chromatography in the presence of glycerol, DTT, ATP and -21. The enzyme consists of 14 subunits as judged by SDS-PAGE. A cDNA clone encoding the ATP synthase alpha subunit has been sequenced. The deduced protein sequence contains a presequence of 45 amino acids which is not present in the mature protein. The mature protein is 58-70% identical to corresponding mitochondrial proteins from other organisms. In contrast to the ATP synthase beta subunit from C. reinhardtii (Franzen and Falk, Plant Mol Biol 19 (1992) 771-780), the protein does not have a C-terminal extension. However, the N-terminal domain of the mature protein is 15-18 residues longer than in ATP synthase alpha subunits from other organisms. Southern blot analysis indicates that the protein is encoded by a single-copy gene.