Mutagenesis of the b'-subunit of Synechocystis sp. PCC 6803 ATP-synthase.

We investigated the F0F1 ATP synthase of the cyanobacterium, Synechocystis sp. PCC 6803. The gene for the F0-subunit b', a peptide probably located at the interface between F0 and F1, has been partially or completely evicted from the bacterial genome. We found that the complete deletion of the subunit was lethal to the cells. However, the subunit could be truncated down to its hydrophobic N-terminal stretch without much harm. Since the gene for b' probably shares a common ancestor with the gene for subunit b and emerged by gene duplication, we propose that b' gathered a new role during evolution, perhaps in the regulation of photophosphorylation.