Thermophiles genome

Analyses of soluble proteins from complete genomes of 20 thermophilic or mesophilic microorganisms revealed that higher amounts of Glu and Asp residues and lower amounts of Gin and Asn residues are present in proteins of thermophiles compared to proteins of mesophiles. " This result suggests that Gin and Asn residues destabilize protein structure at high temperature, possibly through their deamidation. 

The influx of genomic sequence information has led to the concept of structural proteomics, the determination of protein structures on a genome-wide scale. A structural proteomic project used the sequenced genome of the thermophilic Methanobacterium thermoautotrophicum as a source of targets for structure determination.As expected, proteins from M. thermoautotrophicum possess high thermostability with a transition midpoint temperature between 68 and 98 °C. Small proteins were C- and N-labelled and their solution structures were solved using multinuclear and multidimensional NMR spectro-scopy. The project was also extended to some proteins from Thermotoga maritima ... 

Figure 11.5 Prokaryotic genome size distribution (N = 641). Open boxes, free-living prokaryotes grey boxes, obligate parasites black boxes, thermophiles boxes with horizontal lines, endosymbionts. (Modified from Islas etal, 2004.)...

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... 

The primary structure of AspAT from Thermophilic bacillus was determined from cDNA sequence.24 Sequence information of an N-terminal portion of the native enzyme and 19 tryptic peptide fragments, recovered from HPLC, was obtained from gas phase sequencer analyses. Based on such sequence information, four oligonucleotide probes were prepared. cDNA encoding AspAT was cloned by screening restriction enzyme fragments from genomic cDNA of Thermophilic bacillus species YM-2. Amino acid sequence of Thermophilic bacillus AspAT deduced from cDNA was confirmed by the sequences made available by gas phase sequencer analysis. 

Anthramycin is a benzodiazepine alkaloid with potent antitumor and antibiotic activity produced by the thermophilic actinomycete Streptomyces refuineus sbsp. thermotolerans. Using a genome-scanning approach, the biosynthesis was found to involve condensation of 4 methyl-3-hydroxy anthranilic acid 136 and a... 

Recent computational studies of thermophilic adaptation described in this article make use of genomic/proteomic data (32, 43, 53, 62), simulations of model lattice proteins (62), and off-lattice all-atom simulations of natural proteins (43, 53). High-throughput analysis reveals signals of novel mechanisms of protein [entropic mechanism (53)] and DNA [purine-purine base stacking (32)] thermostability and urges us to consider... 

Archaebacteria exhibit different sensitivities to aphidicolin (Table 3) growth of halobacteria and of some methanogens is completely or partially inhibited with 20 pg/ml of aphidicolin, whereas that of other methanogens and of S. acidocaldarius, the only thermophile tested, is resistant [124—128]. In the case of H. halobium, aphidicolin specifically inhibits in vivo DNA replication and induces cell filamentation [124,125]. This result indicates that the target of aphidicolin in halobacteria is implicated in the replication of the genome. 

No direct relationship exists between the optimal growth temperature of the archaeal thermophiles and their genomic G+C content. However, for the large rRNAs, the G+C content increases directly with optimal growth temperature and, at the highest temperatures, the C content increases relatively more than the G content, which suggests that G-U pairs may be converted to G-C pairs. 

La, D Silver, M Edgar, R. C and Livesay, D. R. (2003) Using motif-based methods in multiple genome analyses a case study comparing orthologous mesophilic and thermophilic proteins. Biochemistry 42, 8988-8998. 

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