Gyrases are A2B2 heterotetramers in which the B subunits bind and hydrolyze ATP and the A subunits mediate the double-strand cleavage, strand passage, and reunion reactions.
The eukaryotic type II topoisomerases are homologous to gyrases but with their A and B subunits fused so that they are homodimers.
#Unit 2. Cellular Organization#Structure of chromatin and chromosomes#Part B Pointers
