Purification and properties of an extremely thermostable membrane-bound sulfur-reducing complex from the hyperthermophilic Pyrodictium abyssi


  • Correspondence to R. Dirmeier, Lehrstuhl für Mikrobiologie, Universitätsstrasse 31, D-93053 Regensburg, Germany

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  • Abbreviations. EPPS, 4-(2-hydroxyethyl)-1-piperazinepropane sulfonic acid; HQNO, 2-n-heptyl-4-hydroxyquinoline N-oxide.


The chemolithoautotrophic archaeon Pyrodictium abyssi isolate TAG 11 gains energy by reducing sulfur with H2 to H2S. From this hyperthermophile, a sulfur-reducing complex catalyzing this reaction was purified 13.5-fold. The native complex exhibited a brownish-yellow colour and showed an apparent molecular mass of 520 kDa. SDS/PAGE revealed the presence of nine different major polypeptides with apparent molecular masses of 82, 72, 65, 50, 47, 42, 40, 30 and 24 kDa. The native complex contained 50−55 mol acid-labile sulfur, 50−55 mol iron, 1.6 mol nickel, 1.2 mol copper, 2.8 mol cytochrome b and 0.3 mol cytochrome c (all per mol native complex). The temperature optimum of the H2 : sulfur oxidoreductase complex was 100 +C, which is consistent with the physiological growth optimum of the native organism. The complex is extremely heat stable. During 5 h incubation at 100 +C, no decrease in H2S-forming activity could be observed.