A comparison of an ATPase from the archaebacterium Halobacterium saccharovorum with the F1 moiety from the Escherichia coli ATP synthase.
A purified ATPase associated with membranes from Halobacterium saccharovorum was compared with the F1 moiety from the Escherichia coli ATP synthase. The halobacterial enzyme was composed of two major (I and II) and two minor subunits (III and IV), whose molecular masses were 87 kDa, 60 kDa, 29 kDa and 20 kDa, respectively. The isoelectric points of these subunits ranged from 4.1 to 4.8, which in the case of the subunits I and II was consistent with the presence of an excess of acidic amino acids (20-22 mol/100 mol). Peptide mapping of subunits I and II denatured with sodium dodecyl sulfate showed no relationship between the primary structures of the individual halobacterial subunits or similarities to the subunits of the F1 ATPase from E. coli. Trypsin inactivation of the halobacterial ATPase was accompanied by the partial degradation of the major subunits. This observation, taken in conjunction with molecular masses of the subunits and the native enzyme, was consistent with the previously proposed stoichiometry of 2:2:1:1. These results suggest that H. saccharovorum, and possibly, halobacteria in general, possess an ATPase which is unlike the ubiquitous F0F1 ATP synthase.
Stan-Lotter
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Planetary Biology Branch, Ames Research Center, Moffett Field, California 94035.
Hochstein
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D000251:Adenosine Triphosphatases / Q000032:analysis*; D000596:Amino Acids / Q000032:analysis; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000201:enzymology*; D006217:Halobacterium / Q000201:enzymology*; D007525:Isoelectric Focusing; D008970:Molecular Weight; D010449:Peptide Mapping; D006180:Proton-Translocating ATPases / Q000032:analysis*; D014357:Trypsin
D000596:Amino Acids; D014357:Trypsin; D000251:Adenosine Triphosphatases; D006180:Proton-Translocating ATPases