Helicase-appended topoisomerases: new insight into the mechanism of directional strand transfer.

ABSTRACT: DNA strand passage through an enzyme-mediated gate is a key step in the catalytic cycle of topoisomerases to produce topological transformations in DNA. In most of the reactions catalyzed by topoisomerases, strand passage is not directional; thus, the enzyme simply provides a transient DNA gate through which DNA transport is allowed and thereby resolves the topological entanglement. When studied in isolation, the type IA topoisomerase family appears to conform to this rule. Interestingly, type IA enzymes can carry out directional strand transport as well. We examined here the biochemical mechanism for directional strand passage of two type IA topoisomerases: reverse gyrase and a protein complex of topoisomerase III alpha and Bloom helicase. These enzymes are able to generate vectorial stra

SUBMITTER: Plank J 

PROVIDER: S-EPMC2781472 | biostudies-literature | 2009 Nov

REPOSITORIES: biostudies-literature