2Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia
* To whom correspondence should be addressed.
Received March 19, 2009; Revision received April 9, 2009
DNA topoisomerases are enzymes responsible for regulation of genomic DNA supercoiling. They participate in essential processes of cells such as replication, transcription, recombination, repair, etc., and they are necessary for normal functioning of the cells. Topoisomerases alter the topological state of DNA by either passing one strand of the helix through the other strand (type I) or by passing a region of duplex DNA through another region of duplex DNA (type II). Type I DNA topoisomerases are subdivided into enzymes that bind to the 5′- (type IA) or 3′-phosphate group (type IB) during relaxation of the cleavable DNA. This review summarizes the literature on type IA DNA topoisomerases. Special attention is given to particular properties of their structure and mechanisms of functioning of these enzymes.
KEY WORDS: type IA DNA topoisomerases, structure, reaction mechanism