Organization and nucleotide sequence of the atp genes encoding the ATP synthase from alkaliphilic Bacillus firmus OF4

The atp operon from the extreme alkaliphile Bacillus firmus OF4 was cloned and sequenced, and shown to contain genes for the eight structural subunits of the ATP synthase, preceded by a ninth gene predicted to encode a 14 kDa hydrophobic protein. The arrangement of genes is identical to that of the atp operons from Escherichia coli, Bacillus megaterium, and thermophilic Bacillus PS3. The deduced amino acid sequences of the subunits of the enzyme are also similar to their homologs in other ATP synthases, except for several unusual substitutions, particularly in the a and c subunits. These substitutions are in domains that have been implicated in the mechanism of proton translocation through F0-ATPase, and therefore could contribute to the gating properties of the alkaliphile ATP synthase or its capacity for proton capture.