title: A highly processive topoisomerase I: studies at the single-molecule level.
abstract: Amongst enzymes which relieve torsional strain and maintain chromosome supercoiling, type IA topoisomerases share a strand-passage mechanism that involves transient nicking and re-joining of a single deoxyribonucleic acid (DNA) strand. In contrast to many bacterial species that possess two type IA topoisomerases (TopA and TopB), Actinobacteria possess only TopA, and unlike its homologues this topoisomerase has a unique C-terminal domain that lacks the Zn-finger motifs characteristic of type IA enzymes. To better understand how this unique C-terminal domain affects the enzyme's activity, we have examined DNA relaxation by actinobacterial TopA from Streptomyces coelicolor (ScTopA) using real-time single-molecule experiments. These studies reveal extremely high processivity of ScTopA not described previously for any other topoisomerase of type I. Moreover, we also demonstrate that enzyme processivity varies in a torque-dependent manner. Based on the analysis of the C-terminally truncated ScTopA mutants, we propose that high processivity of the enzyme is associated with the presence of a stretch of positively charged amino acids in its C-terminal region.
authors.affiliation: Faculty of Biotechnology, University of Wrocław, Joliot-Curie 14A, 50-383 Wrocław, Poland marcin.szafran@uni.wroc.pl.
authors.forename: Marcin Jan
authors.initials: MJ
authors.lastname: Szafran
authors.affiliation: Institut Jacques Monod, CNRS UMR 7592, University Paris Diderot, Sorbonne Paris Cité, F-75205 Paris, France strick.terence@ijm.univ-paris-diderot.fr.
authors.forename: Terence
authors.initials: T
authors.lastname: Strick
authors.affiliation: Faculty of Biotechnology, University of Wrocław, Joliot-Curie 14A, 50-383 Wrocław, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Strzałka
authors.affiliation: Faculty of Biotechnology, University of Wrocław, Joliot-Curie 14A, 50-383 Wrocław, Poland Ludwik Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Weigla 12, Wrocław, 53-114, Poland.
authors.forename: Jolanta
authors.initials: J
authors.lastname: Zakrzewska-Czerwińska
authors.affiliation: Faculty of Biotechnology, University of Wrocław, Joliot-Curie 14A, 50-383 Wrocław, Poland Ludwik Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Weigla 12, Wrocław, 53-114, Poland.
authors.forename: Dagmara
authors.initials: D
authors.lastname: Jakimowicz
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D004264:DNA Topoisomerases, Type I / Q000737:chemistry / Q000378:metabolism*; D004278:DNA, Superhelical / Q000378:metabolism; D048372:Streptomyces coelicolor / Q000201:enzymology; D019415:Torque
chemical_list: D001426:Bacterial Proteins; D004278:DNA, Superhelical; D004247:DNA; D004264:DNA Topoisomerases, Type I