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  • Title: Cloning and sequencing of the gene coding for topoisomerase I from the extremely thermophilic eubacterium, Thermotoga maritima.
    Author: Bouthier de la Tour C, Kaltoum H, Portemer C, Confalonieri F, Huber R, Duguet M.
    Journal: Biochim Biophys Acta; 1995 Dec 27; 1264(3):279-83. PubMed ID: 8547314.
    Abstract:
    A 2767 bp fragment containing a gene coding for a topoisomerase I from the extremely thermophilic eubacterium Thermotoga maritima (Tm TopA) has been cloned and sequenced. The protein is composed of 633 amino acids with a calculated molecular mass of 72,695 Da. It shares significant similarity with the topoisomerases I of mesophilic eubacteria. The highest score is obtained with Bacillus subtilis (44% identity); in particular, T. maritima and B. subtilis possess an insertion of 7-8 amino acids in the vicinity of the active site, that is absent in topoisomerases of other organisms. A specific feature of T. maritima topoisomerase I is its low cysteine content compared to its mesophilic homologs. It contains 5 cysteine residues, of which 4 could constitute a zinc finger motif. Finally, analysis of the regions flanking the gene reveals that Tm TopA is surrounded by two other ORFs, suggesting the occurrence of a polycistronic transcriptional unit.
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