Relationship of the Membrane ATPase from Halobacterium saccharovorum to Vacuolar ATPases

Polyclonal antiserum against subunit A (67 kDa) of the vacuolar ATPase from Neurospora crassa reacted with subunit I (87 kDa) from a membrane ATPase of the extremely halophilic archaebacterium Halobacterium saccharovorum. The halobacterial ATPase was inhibited by nitrate and N-ethylmaleimide; the extent of the latter inhibition was diminished in the presence of adenosine di- or triphosphates. 4-Chloro-7-nitrobenzofurazan in- hibited the hatobacterial ATPase also in a nucleotide- protectable manner; the bulk of inhibitor was associated with subunit II (60 kDa). The data suggested that this halobacterial ATPase may have conserved structural features from both the vacuotar and the F-type ATPases.