>TIGR01054 rgy reverse gyrase; InterPro: IPR005736 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 I topoisomerases are ATP-independent enzymes (except for reverse gyrase), and can be subdivided according to their structure and reaction mechanisms: type IA (bacterial and archaeal topoisomerase I, topoisomerase III and reverse gyrase) and type IB (eukaryotic topoisomerase I and topoisomerase V). These enzymes are primarily responsible for relaxing positively and/or negatively supercoiled DNA, except for reverse gyrase, which can introduce positive supercoils into DNA. Reverse gyrase is a type IA topoisomerase that is unique among these enzymes in its requirement for ATP. Reverse gyrase is a hyperthermophile-specific enzyme that acts as a renaturase by positively supercoiling DNA, and by annealing complementary single-strand circles . Hyperthermophilic organisms must protect themselves against heat-induced degradation, and reverse gyrase acts to reduce the rate of double-strand DNA breakage, a function that does not require ATP hydrolysis and which is independent of its positive supercoiling abilities. Reverse gyrase achieves this by recognising nicked DNA and recruiting a protein coat to the site of damage . More information about this protein can be found at Protein of the Month: DNA Topoisomerase .; GO: 0003677 DNA binding, 0003916 DNA topoisomerase activity, 0006265 DNA topological change, 0006268 DNA unwinding during replication, 0005694 chromosome.

Probab=92.10  E-value=0.05  Score=34.63  Aligned_cols=29  Identities=28%  Similarity=0.308  Sum_probs=15.3

Q ss_pred             CEEEEECCC-----CHHHHHHHHHHHHHHHHCCCCEE
Q ss_conf             619984475-----31579999999999851468479
Q gi|254780619|r  219 AVSLISGVT-----GSGKTEVYLEIVAAVLHLGKQVL  250 (731)
Q Consensus       219 ~~~LL~GvT-----GSGKTEVYl~li~~~L~~GkqvL  250 (731)
T Consensus       560 ~~ylvvpD~~tYiQASGRT---SRl~aGGlTkGlS~V  593 (1843)
T TIGR01054       560 KLYLVVPDVKTYIQASGRT---SRLYAGGLTKGLSVV  593 (1843)
T ss_pred             EEEEEECCCCCCCCCCCHH---HHHHHHHHHHCCEEE
T ss_conf             2599966877442467415---665542323053489