Complete DNA sequence of the atp operon of the sodium-dependent F1Fo ATP synthase from Ilyobacter tartaricus and identification of the encoded subunits

The atp operon of Ilyobacter tartaricus, strain DSM 2382, was completely sequenced using conventional and inverse polymerase chain reaction (i-PCR) techniques. It contains nine open reading frames that were attributed to eight structural genes of the F(1)F(o) ATP synthase and the atpI gene, which is not part of the enzyme complex. The initiation codons of all atp genes, except that of atpB coding for the a subunit, were identified by the corresponding N-terminal amino acid sequence. The hydrophobic a subunit was identified by MALDI mass spectrometry. The atp genes of I. tartaricus are arranged in one operon with the sequence atpIBEFHAGDC comprising 6,992 base pairs with a GC content of 38.1%. The F(1)F(o) ATP synthase of I. tartaricus has a calculated molecular mass of 510 kDa and includes 4,810 amino acids. The gene sequences and products reveal significant identities to atp genes of other Na(+)-translocating F(1)F(o) ATP synthases, especially in the F(o) subunits a and c which are directly involved in ion translocation.