The atpIBEXF operon coding for the F0 sector of the ATP synthase from the purple nonsulfur photosynthetic bacterium Rhodobacter capsulatus

The atpIBEXF operon coding for the F0 sector of the ATP synthase from Rhodobacter capsulatus was cloned and sequenced. The genes for the five subunits were present in the order: atpI (subunit I), atpB (subunit a), atpE (subunit c), atpX (subunit b'), and atpF (subunit b). The transcription initiation site was defined by primer-extension analysis. A duplicated and divergent copy of the b subunit gene (subunit b') was present. This duplication is found only in photosynthetic prokaryotes and in plant chloroplasts. F0 deletion mutants formed tiny colonies during anaerobic growth in the dark but could not sustain continuous growth. Based on the results of the present work, we conclude that a functioning ATP synthase is essential for normal growth under all conditions tested.