title: A topA intein in Pyrococcus furiosus and its relatedness to the r-gyr intein of Methanococcus jannaschii.
abstract: A new intein coding sequence was found in a topA (DNA topoisomerase I) gene by cloning and sequencing this gene from the hyperthermophilic Archaeon Pyrococcus furiosus. The predicted Pfu topA intein sequence is 373 amino acids long and located two residues away from the catalytic tyrosine of the topoisomerase. It contains putative intein sequence blocks (C, E, and H) associated with intein endonuclease activity, in addition to intein sequence blocks (A, B, F, and G) that are necessary for protein splicing. This DNA topoisomerase I intein is most related to a reverse gyrase intein from the methanogenic Archaeon Methanococcus jannaschii. These two inteins share 31% amino acid sequence identity and, more importantly, have the same insertion sites in their respective host proteins. It is suggested that these two inteins are homologous inteins present in structurally related, but functionally distinct, proteins, with implications on intein evolution and intein homing.
authors.affiliation: Biochemistry Department, Dalhousie University, Halifax, Nova Scotia, B3H 4H7, Canada.
authors.forename: I C
authors.initials: IC
authors.lastname: Chute
authors.forename: Z
authors.initials: Z
authors.lastname: Hu
authors.forename: X Q
authors.initials: XQ
authors.lastname: Liu
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry; D003001:Cloning, Molecular; D004264:DNA Topoisomerases, Type I / Q000737:chemistry*; D004250:DNA Topoisomerases, Type II / Q000737:chemistry*; D019143:Evolution, Molecular; D017017:Methanococcus / Q000201:enzymology*; D008969:Molecular Sequence Data; D011499:Protein Processing, Post-Translational / Q000502:physiology; D019154:Protein Splicing / Q000235:genetics*; D019711:Pyrococcus / Q000201:enzymology*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D001426:Bacterial Proteins; C041813:DNA reverse gyrase; D004264:DNA Topoisomerases, Type I; D004250:DNA Topoisomerases, Type II