Conformational Changes in Type IA Topoisomerases Facilitate Strand Passage.

Type IA topoisomerases are present in all kingdoms of life and are responsible for simplifying torsionally strained DNA structures during fundamental cellular processes. The common model for this simplification is based upon the concept of passage of an intact DNA strand through a transient cut in another single DNA strand. This process requires the protein to undergo several conformational changes. In this review, we discuss these conformational changes across the strand passage cycle from DNA binding through opening and closing of a protein mediated DNA gate. We also examine the involvement of the diverse C-terminal domains of these enzymes during strand-passage and current open questions in the field.