Prokaryotic organisms, thermophilic

Let us now come back to nature as it is, and look at the size of the smallest organisms. Figure 11.5 compares the genome size distribution, calculated under a series of assumptions (Islas etal., 2004), of free-living prokaryotes, obligate parasites, thermophiles, and endosymbionts. The values of DNA content of free-hving... 

Fig. 5.2. Subunit organization of prokaryotic ATPase. The subunit stoicheiometry is based on that of thermophilic FqF, [51]. /S y 8 a b c = 3 3 l l l l 2 6. The F, portion forms a plug through the phospholipid bilayer. The c subunit assumes a hairpin shape [67].

MnSODs and FeSODs from most procaryotic organisms are dimeric while MnSODs from mitochondria and some thermophilic bacteria are tetrameric [21]. However, mitochondrial MnSOD from Caenorhahditis elegans was found to be dimeric [22]. Eukaryotic MnSOD is a tetrameric protein encoded in the nucleus, synthesized in the cystosol, and imported post-translationally into the mitochondrial matrix. The 25 kDa precursor protein has a mitochondrial transit peptide that is cleaved to produce the mature 22 kDa subunit. The mature protein exists as a tetramer, each subunit containing one Mn ion. The mitochondrial MnSOD primary sequences are highly homologous to the prokaryotic Mn- and FeSOD, but has no resemblance to the CuZnSODs [23]. In MnSODs and FeSODs, the metal ions are coordinated by three His N atoms and one Asp O atom [24]. 

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