Resolution of the Aerobic Respiratory System of the Thermoacidophilic Archaeon, Sulfolobus sp. Strain 7:

Abstract

The aerobic respiratory system of the thermoacidophilic archaeon, Sulfolobus sp. strain 7, is unusual in that it consists of only a-and b-type cytochromes but no c-type cytochromes. In previous studies, a novel cytochrome oxidase a 583 -aa 3 subcomplex has been purified, which showed a ferrocytochrome c oxidase but no caldariellaquinol oxidase activity (Wakagi, T., Yamauchi, T., Oshima, T., Mü ller, M., Azzi, A., and Sone, N. (1989) Biochem. Biophys. Res. Commun. 165, 1110 -1114). We show here that the cytochrome subcomplex could be copurified with a non-CO-reactive cytochrome b 562 as a novel terminal oxidase "supercomplex," which also contained a Rieske-type FeS cluster at g y ‫؍‬ 1.89. It contained one copper and all four heme centers detectable in the archaeal membranes by the low temperature spectrophotometry and the potentiometric titration: cytochromes b 562 (؉146 mV), a 583 (؉270 mV), and aa 3 (؉117 and ؉325 mV). The presence of one copper atom indicates that it contains the conventional heme a 3 -Cu B binuclear center for reducing molecular oxygen. In conjunction with the presence of a Rieske-type FeS center, inhibitor studies suggest that the terminal oxidase segment of the respiratory chain of Sulfolobus sp. strain 7 is a functional fusion of respiratory complexes III and IV, where cytochrome b 562 and the Rieske-type FeS center probably play a central role in the oxidation of caldariellaquinol. This archaeal terminal oxidase supercomplex reconstitutes the in vitro succinate oxidase respiratory chain for the first time together with caldariellaquinone and the purified cognate succinate:caldariellaquinone oxidoreductase complex. The reconstitution system requires caldariellaquinone for the activity, and is highly sensitive to cyanide and 2-heptyl-4-hydroxy-quinoline-N-oxide. These results are also discussed in terms of the evolutionary considerations.

Interaction between Cytochrome caa3 and F1F0-ATP Synthase of Alkaliphilic Bacillus pseudofirmus OF4 Is Demonstrated by Saturation Transfer Electron Paramagnetic Resonance and Differential Scanning Calorimetry Assays

“…Rather, the current results are in line with a growing body of work that now suggests that some mitochondrial electron-transfer complexes specifically interact to form supermolecular structures called supercomplexes in organisms ranging from the yeast Saccharomyces cerevisiae (35,36), beef (19,29,35,37), and plants (38)(39)(40)(41)(42). Similar supermolecular structures have also been described for the respiratory chains of bacteria (43)(44)(45)(46)(47). The roles that have been attributed to respiratory supercomplexes are substrate-channeling, catalytic enhancement, sequestration of reactive intermediates (35), stabilization of protein complexes (48), increasing the capacity of the inner mitochondrial membrane for protein insertion (36), and generating mitochondrial cristae morphology (49).…”

Novel Zinc-containing Ferredoxin Family in Thermoacidophilic Archaea

“…ferredoxin. 7 The presence of a unique zinc center in these ferredoxins might represent a unique evolutionary event in early thermoacidophilic archaea.…”

“…This is also the case in several strictly aerobic archaea, including Sulfolobus sp. strain 7, which contains nearly complete sets of the membrane-bound proteins for aerobic respiration (7,(11)(12)(13)(14)(15)(16), indicating that the central metabolic pathways of aerobic archaea are probably more closely related to the ferredoxin-linked fermentative pathways of anaerobic archaea and bacteria than is the case for the aerobic bacteria and eukarya (e.g. see Iwasaki et al (7)).…”

Engineering a Three-cysteine, One-histidine Ligand Environment into a New Hyperthermophilic Archaeal Rieske-type [2Fe-2S] Ferredoxin from Sulfolobus solfataricus

“…One type displays higher reduction potentials (E m ) 1 of approximately ϩ150 to ϩ490 mV and occurs in proton-translocating respiratory complexes (cytochrome bc 1 /b 6 f complexes and their archaeal homologs without c-type cytochromes), being involved in not only electron transfer but also substrate binding and oxidation at the quinol-oxidizing Q o site (2)(3)(4)(5)(12)(13)(14)(15). The other type displays lower E m values of approximately Ϫ150 to Ϫ50 mV and has been found in a diverse group of bacterial multicomponent terminal oxygenases and soluble Rieske-type ferredoxins (1, 3, 8, 9, 16 -27).…”