>TIGR01052 top6b DNA topoisomerase VI, B subunit; InterPro: IPR005734 DNA topoisomerases regulate the number of topological links between two DNA strands (i.e. change the number of superhelical turns) by catalysing transient single- or double-strand breaks, crossing the strands through one another, then resealing the breaks. These enzymes have several functions: to remove DNA supercoils during transcription and DNA replication; for strand breakage during recombination; for chromosome condensation; and to disentangle intertwined DNA during mitosis , . DNA topoisomerases are divided into two classes: type I enzymes (5.99.1.2 from EC; topoisomerases I, III and V) break single-strand DNA, and type II enzymes (5.99.1.3 from EC; topoisomerases II, IV and VI) break double-strand DNA . Type II topoisomerases are ATP-dependent enzymes, and can be subdivided according to their structure and reaction mechanisms: type IIA (topoisomerase II or gyrase, and topoisomerase IV) and type IIB (topoisomerase VI). These enzymes are responsible for relaxing supercoiled DNA as well as for introducing both negative and positive supercoils . This entry represents subunit B of topoisomerase VI, a type IIB topoisomerase found predominantly in archaea, but also in a few eukayotes, such as the plant Arabidopsis thaliana . This enzyme assembles as a heterotetramer, consisting of two A subunits required for DNA cleavage and two B subunits required for ATP hydrolysis. The B subunit is structurally similar to the ATPase domain of type IIA topoisomerases, but the A subunit is distinct, and instead shares homology with the Spo11 protein that mediates double-strand DNA breaks during meiotic recombination in eukaryotes . Therefore, though related to type IIA topoisomerases, topoisomerase VI may have a distinctive mechanism of action. More information about this protein can be found at Protein of the Month: DNA Topoisomerase .; GO: 0003677 DNA binding, 0003918 DNA topoisomerase (ATP-hydrolyzing) activity, 0006265 DNA topological change, 0006268 DNA unwinding during replication, 0005694 chromosome.

Probab=99.28 E-value=5.3e-11 Score=94.81 Aligned_cols=163 Identities=25% Similarity=0.306 Sum_probs=113.9 Q ss_pred CCCHHHHHHHHHHHHHHHHH-CCCCCEEEEEEC---C-------CC-EEEEEECCCCCCCCCCCCCCCCEEEEEEEEEEE Q ss_conf 55022024436666787776-189976999982---8-------98-399996698434441766578701234545200 Q gi|254780222|r 71 EKALHHLFSEVIDNAMDEVI-AGYANLIEVSLD---G-------NG-FLTVVDNGRGIPVENHPKFPNKSTLEIILTTLH 138 (686) Q Consensus 71 ~~GL~~i~~EIldNavDe~~-~g~~~~I~V~i~---~-------dg-~IsV~ddGrGIPv~~h~k~~~~~~~Elif~~L~ 138 (686) T Consensus 26 iRsL~~~ihElVtNSLDAcEEAGILP~I~v~I~~~g~seGrGGr~HY~v~VEDNGPGIP~~~IP---------kVFGKmL 96 (662) T TIGR01052 26 IRSLTTVIHELVTNSLDACEEAGILPDIKVEIEKIGKSEGRGGRDHYKVVVEDNGPGIPEEYIP---------KVFGKML 96 (662) T ss_pred HHHHHHHHHHHHHCHHHHHHHCCCCCCCEEEEEEECCCCCCCCCCCEEEEEEECCCCCCCCCCC---------CHHHHHC T ss_conf 6889999999971424676643799840589898527778999962079984078899700013---------1320211 Q ss_pred CCCCCCCCCEEEECCCCCHHHHHHHHEEEEEE-----EEEEC--CCEEE--EEEEECCCEECCCEECC-------CCCCC Q ss_conf 24777777415631445388987620321269-----99941--88389--99972794511311216-------76778 Q gi|254780222|r 139 AGGKFDNSTYEISGGLHGVGISVVNALSDELH-----VTVAR--QNTIF--SQKFSRGIPLSPLEKKE-------KVRNK 202 (686) Q Consensus 139 aggnfdd~~yk~sgGlnGvGaklvNalS~~f~-----Vev~r--~gk~y--~q~f~~g~~~~~~~~i~-------~~~~k 202 (686) T Consensus 97 aGSK~h~~--iQSRGqQGiG~sgavL~~Q~TTGKP~~VIs~T~~nGe~~~~~~~l~idV~KNEg~Ivek~eee~~~~~~W 174 (662) T TIGR01052 97 AGSKFHRI--IQSRGQQGIGISGAVLYAQITTGKPVKVISSTGENGEIYAKKVKLKIDVKKNEGEIVEKGEEEWEKPGSW 174 (662) T ss_pred CCCEEEEE--EECCCCHHHHHHHHHHHHHHCCCCCEEEEECCCCCCCEEEEEEEEEEEEEECCCEEEECCCEEECCCCCC T ss_conf 14400033--2067851567999999876147984588805686756158999999853325873430121014179981 Q ss_pred CCEEEEEEECHHHEECCCCCCHHHHHHHHHHHHHCCCCCEEEEECC Q ss_conf 8539999984243200122228999998888753057735999516 Q gi|254780222|r 203 RGTRITFRPDPKIFGDKAGFDAARLLKMTQSKAYLSGRVKTCWSCD 248 (686) Q Consensus 203 ~GT~ItF~PD~~iFg~~~~~d~~~l~~rl~~~A~L~~gl~i~~~~~ 248 (686) T Consensus 175 ~GTriEle~~~v~y----~~~~~g~yEYlrrt~~anPHA~I~l~~P 216 (662) T TIGR01052 175 RGTRIELEVKDVSY----RRSKQGVYEYLRRTAVANPHAKIVLVEP 216 (662) T ss_pred EEEEEEEEEECCEE----ECCCCCHHHHHHHHHHHCCCCEEEEECC T ss_conf 36899999822255----3111344589899875186408998869

HHsearch alignment for GI: 254780222 and conserved domain: TIGR01052