Structural studies of E. coli topoisomerase III-DNA complexes reveal a novel type IA topoisomerase-DNA conformational intermediate.

ABSTRACT: Escherichia coli DNA topoisomerase III belongs to the type IA family of DNA topoisomerases, which transiently cleave single-stranded DNA (ssDNA) via a 5' phosphotyrosine intermediate. We have solved crystal structures of wild-type E. coli topoisomerase III bound to an eight-base ssDNA molecule in three different pH environments. The structures reveal the enzyme in three distinct conformational states while bound to DNA. One conformation resembles the one observed previously with a DNA-bound, catalytically inactive mutant of topoisomerase III where DNA binding realigns catalytic residues to form a functional active site. Another conformation represents a novel intermediate in which DNA is bound along the ssDNA-binding groove but does not enter the active site, which remains in a catalytical

SUBMITTER: Changela A 

PROVIDER: S-EPMC1885233 | biostudies-literature | 2007 Apr

REPOSITORIES: biostudies-literature