Thermoacidophiles

In summary, it appears that the protein has to adopt the correct fold before the Rieske cluster can be inserted. The correct folding will depend on the stability of the protein the Rieske protein from the thermoacidophilic archaebacterium Sulfolobus seems to be more stable than Rieske proteins from other bacteria so that the Rieske cluster can be inserted into the soluble form of the protein during expression with the help of the chaperonins. If the protein cannot adopt the correct fold, the result will be either no cluster or a distorted iron sulfur cluster, perhaps using the two cysteines that form the disulfide bridge in correctly assembled Rieske proteins. 

Remonsellez F, A Orell, CA Jerez (2006) Copper tolerance of the thermoacidophilic archaeon Sulfolobus metallicus possible role of polyphosphate metabolism. Microbiology (UK) 152 59-66. 

Luo J, Fukuda E, Takase H et al (2009) Identification of the lysine residue responsible for coenzyme A binding in the heterodimeric 2-oxoacid ferredoxin oxidoreductase from Sulfo-lobus tokodaii, a thermoacidophilic archaeon, using 4-fluoro-7-nitrobenzofurazan as an affinity label. Biochim Biophys Acta 1794 335-340... 

Ferredoxins from thermoacidophilic archaea such as Thermoplasma acidophi-lum and Sulfolobus sp. contain, in addition to one 3Fe-4S (cluster I) and one 4Fe-4S (cluster II) cluster, one zinc centre tetrahedrally co-ordinated to three histidines in the N-terminal region and to one aspartate in the ferredoxin core domain. These Fds contain an unusually long N-terminal extension region of unknown function, which was not detected in other bacterial type Fds. Upon oxidative degradation of Fd from Sulfolobus sp. strain 7 (Fopt = 80 cluster II is selectively converted into a cubane 3Fe-4S,... 

Isoprenyi glyceryl ethers archaeol-like (archaeol Cm-C ), comprising C20-C25 and C25"C25 homologues (an extreme halophilic, thermoacidophilic, and methanogenic Archaea Kates 1993 caldarchaeol-like (caldarchaeol monocyclic C o-C ), comprising bicyclic structures from thermoacidophilic and methanogenic Archaea Kates 1993. (Archaea in bold ce are not meant to be exclusively marine). 

Lacher, K. Schafer, G. Archaebacterial adenylate kinase from the thermoacidophile Sulfolobus acidocaldarius purification, characterization, and partial sequence. Arch. Biochem. Biophys., 302, 391-397 (1993)... 

Okajima, T. Kitaguchi, D. Fujii, K. Matsuoka, H. Goto, S. Uchiyama, S. Kobayashi, Y Tanizawa, K. Novel trimeric adenylate kinase from an extremely thermoacidophilic archaeon, Sulfolobus solfataricus molecular cloning, nucleotide sequencing, expression in Escherichia coli, and characterization of the recombinant enzyme. Biosci. Biotechnol. Biochem., 66, 2112-2124 (2002)... 

The 3-hydroxypropionate/4-hydroxybutyrate cycle functions in autotrophic Sul-folobales (Crenarchaeota) [35-37]. These are extreme thermoacidophiles from volcanic areas which grow best at a pH of about 2 and temperatures of 60 to 90 °C. 

Moracci, M., Capalbo, L., Ciaramella, M., and Rossi, M. (1996) Identification of two glutamic acid residues essential for catalysis in the p-glycosidase from the thermoacidophilic archaeon Sulfolobus solfataricus. Protein Eng. 12, 1191-1195. 

Figure 7.29. Structures of some membrane lipids found in the Archaea. These lipids are able to form stable monolayers. (A) A tetraether lipid, diphytanylglycosylglycerol. (B) A tetraether lipid of an extreme thermoacidophile, Sulfolobus sulfataricus. C40H72-so denotes the two biphytanyl chains (including 0 to 3 cyclopentanes). In thermophilic members of the Archaea, the ratio of tetraether lipids to diether lipids rises with increasing temperature. (Figure modified after Hazel and Williams, 1990.)...

I. N. Stadnichuk, L. R. Semenova, G. P. Smirnova, and A. I. Usov, A highly branched storage polyglucan in the thermoacidophilic red microalga Galdieria maxima cells, Prikl. Biokhim. Mikrobiol., 43 (2007) 88—93 (in Russian). 

Hexose catabolism has been studied in detail in two thermophilic archaebacterial genera, Sulfolobus and Thermoplasma, organisms which are phenotypically close (they are both thermoacidophiles) but phylogenetically distinct. Interestingly, in both genera a further modification of the Entner-Doudoroff pathway has been found. 

With regard to possible mechanisms for the regeneration of NAD(P) and the possible concomitant synthesis of ATP in thermoacidophiles, an ATPase involved in oxidative phosphorylation in S. acidocaldarius has been found [17-19]. However, no proton-translocating ATPase has been identified in Tp. acidophilum, although a membrane-bound enzyme, proposed to function as a sulphate-exporting translocase, has been reported [20]. 

It should be noted that the extreme halophiles contain only archaeol-derived lipids, the methanogens contain both archaeol-and caldarchaeol-derived lipids, in about 2 1 to 1 1 proportion, respectively, and the thermoacidophiles contain largely caldarchaeol- and nonitolcaldarchaeol-derived lipids, with a maximum of 1-10%a of archaeol-derived lipids[4,10,21,27,28]. 

Fig. 2. Dibiphytanyidiglyceroltetraether (2, caldarchaeol), dibiphytanyl glycerol nonitol tetraether (2A, nonitolcaldarchaeol), and various cyclized derivatives (2B-2I, cyclized caldarchaeols and nonitolcaldarchaeols) core lipids in thermoacidophiles and some methanogens [10,12,20].

Variants of the dibiphytanyldiglyceroltetraether (2) core-lipid structures are also found in some archaea for example, species of the thermoacidophilic Sulfolobus genus contain lipids derived from a dibiphytanylglycerol nonitoltetraether (nonitolcaldarchaeol, structure 2A, Fig. 2) as well as from dibiphytanyldiglyceroltetraether (caldarchaeol, 2) [10,12,17,18,20]. Both caldarchaeol and nonitolcaldarchaeol may contain one to four cyclopentane rings in each of the C40 biphytanyl groups (structures 2B-2I, Fig. 2) [10,12],... 

The taxonomical classification of thermoacidophiles is not as complex as that of the methanogens eight genera are known so far, distributed among four orders Thermoplasmatales, Sulfolobales, Thermoproteales and Thermococcales. Only a relatively small number of thermoacidophiles and thermococcales have been examined... 

Klimczak et al. [139] have purified to homogeneity a monomeric DNA polymerase which is resistant to aphidicolin from the thermoacidophile S. acidocaldarius [ 2i9] and the methanogen M. thermoautotrophicum[ AO]. The DNA polymerase from... 

T. acidophilum, were purified to homogeneity in our laboratory [141,142]. Depending on the strain, the molecular mass of these monomeric DNA polymerases lies in the range of 70-100 kDa, which is close to the molecular mass of the aphidicolin-sensitive DNA polymerases isolated from other archaebacterial species. These enzymes are associated with a 3 to 5 exonuclease activity that could be involved in a proofreading mechanism (refs. [139,140,142], and our laboratory, unpublished results). In addition, the DNA polymerase from M thermoautotrophicum is associated with a 5 to 3 exonuclease activity [140], as is the case for eubacterial DNA polymerase I. In contrast, this activity has not been detected with DNA polymerases of thermoacidophiles. It has been shown that the 100 kDa DNA polymerase from S. acidocaldarius can be used in PCR [143,144]. 

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