Cloning and sequencing of the gene coding for topoisomerase I from the extremely thermophilic eubacterium, Thermotoga maritima.
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.
Laboratoire d'Enzymologie des Acides Nucléiques, Institut de Génétique et Microbiologie, URA 1354, Université Paris-Sud, Orsay, France.
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Bouthier de la Tour
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Kaltoum
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Portemer
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Confalonieri
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Huber
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Duguet
D000595:Amino Acid Sequence; D001483:Base Sequence; D004264:DNA Topoisomerases, Type I / Q000235:genetics*; D005798:Genes, Bacterial; D006089:Gram-Negative Anaerobic Bacteria / Q000235:genetics*; D008969:Molecular Sequence Data
D004264:DNA Topoisomerases, Type I