Topi participates in the relaxation of negative super coils and has also been implicated in knotting and unknotting DNA and in linking complementary rings of single-stranded DNA into double-stranded rings .
The relaxation process catalysed by the enzyme essentially consists of a transient break of a segment of single-stranded DNA, followed by passing an intact strand of DNA through the gate (type I-A) or allowing rotation of the broken strand around the intact strand (type I-B), with final rejoining of the broken segment. Topi has several distinct features. Unlike type II enzymes, it appears to fully perform its functions as a monomer. In addition, it does not require ATP hydrolysis to catalyze the complex topological rearrangements of DNA.
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