ATP synthesis at 100 degrees C by an ATPase purified from the hyperthermophilic archaeon Pyrodictium abyssi

The chemolithoautotrophic archaeon Pyrodictium abyssi isolate TAG 11 lives close to 100 degrees C and gains energy by sulfur respiration, with hydroge n as electron donor. From the membranes of this hyperthermophile, an ATPase complex was isolated. The purified enzyme consists of six major polypeptid es, the 67, 51, 41, 26 and 22 kDa subunits composing the AF(1) headpiece, a nd the 7 kDa proteolipid of the AF(0) component. The headpiece of the enzym e restored the formation of ATP during sulfur respiration in membrane vesic les from which it had been removed by low salt treatment. Characteristics o f the reconstituted activity suggest that the same enzyme is responsible fo r ATP formation in untreated membranes. ATP formation was neither sensitive to ionophores and uncouplers, nor to dicyclohexyl carbodiimide, but depend ed on closed vesicles. Both ATPase activity (up to 2 mu mol per min and mg protein) as well as ATP formation (up to 0.4 mu mol per min and mg membrane protein) were highest at 100 degrees C. A P/e2 ratio of close to one can b e estimated for sulfur respiration with hydrogen. In addition to ATP, autor adiographic detection revealed the formation of high quantities of P-33(i)- labeled ADP and of another compound not identified so far. (C) 2000 Federat ion of European Biochemical Societies.