lecture5 - Topoisomerases Enzymes that alter winding...

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Topoisomerases Enzymes that alter winding properties of DNA Important in DNA replication and packaging Two general classes Type I (Topoisomerase I; a/k/a nicking-closing enzyme) --change L in steps of 1 by producing transient single-strand breaks in one strand of DNA helix Type II (Topoisomerase II) --change L in steps of 2 by producing transient double-strand breaks in DNA helix
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E. coli topo I • relaxes neg. sc DNA Eucaryotic topo I • relaxes - and + sc DNA • catenates (interlocks) ds circular DNAs or separates catenates if at least 1 circle is nicked • induces knots in ss circle • forms ds circles from ss circles E. coli topo II •a/k/a/ DNA gyrase •relaxes neg. sc DNAs •introduces neg sc in circular DNA Eucaryotic topo II •relaxes both pos and neg sc •cannot introduce sc •catenates/decatenates, but no nicks are required •knots/unkots ds circles Topoisomerases
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Relaxation of sc Knotting/Unknotting Circular Duplex Formation Decatenantion of nicked Catenanes + Topological Conversions Catalyzed by Topo I
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Relaxation of sc (Introduction of sc for DNA gyrase only) Catenation/Decatenation Knotting/Unknotting Topological Conversions Catalyzed by Topo II
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This note was uploaded on 04/06/2010 for the course BCH BCH 453 taught by Professor Heminway during the Spring '10 term at N.C. State.

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lecture5 - Topoisomerases Enzymes that alter winding...

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