| Abstrakt: |
The discovery of a V-type ATPase in the gram-negative bacterium Thermus thermophilusHB8 (Yokoyama et al., J. Biol. Chem. 265, 21946, 1990) was unexpected, since only eukaryotic endomembranes and archaea were thought to contain this enzyme complex, and horizontal gene transfer was suggested to explain the finding. We examined membrane-associated ATPases from representatives of several groups of the genus Thermus. The enzymes were extracted with chloroform and purified by ion exchange chromatography or native gel electrophoresis. One novel Islandic isolate, T. scotoductusSE-1, as well as strain T. filiformisfrom New Zealand, possessed F-ATPases, as judged by the typical five subunit composition of the F1-moiety, sensitivity to azide, insensitivity to nitrate and a strong crossreaction with antibodies against the F1-ATPase from E. coll. In addition, N-terminal amino acid sequencing of the β subunit from T. scotoductusSE-1 confirmed its homology with β subunits from known F-ATPases. In contrast, the same extraction procedure released a V-ATPase from the membranes of T. thermophilusHB27 and T. aquaticusYT-1. The related species Meiothermus(formerly Thermus) chliarophilusALT-8 also possessed a V-ATPase. All V-ATPases examined in this study contained larger major subunits than F-ATPases, crossreacted with antiserum against subunit A of the V-ATPase from the archaeon Halobacterium saccharovorum, and the N-terminal sequences of their major subunits were homologous to those of other V-ATPases. Sequences of the 16S rRNA gene clearly placed T. scotoductusSE-1, along with other non-pigmented Thermusstrains, as a distinct species close to T. aquaticus. Our results suggested that at least two members of the genus, T. scotoductusSE-1 and T. filiformis, contain an F-ATPase, whereas several others possess a V-ATPase. These data could indicate a greater diversity of the genus Thermusthan was previously thought. Alternatively, the genus may consist of species where horizontal gene transfer has occurred and others, where it has not. |
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