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DNA binding induces conformational transition within human DNA topoisomerase I in solution
Author(s) -
Oleinikov Vladimir,
Sukhanova Alyona,
Mochalov Konstantin,
Ustinova Olga,
Kudelina Irina,
Bronstein Igor,
Nabiev Igor
Publication year - 2002
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.10141
Subject(s) - chemistry , dna , circular dichroism , topoisomerase , crystallography , oligonucleotide , footprinting , hydrogen bond , stereochemistry , molecule , biochemistry , base sequence , organic chemistry
Abstract We employed Raman and circular dichroism (CD) spectroscopy to probe the molecular structure of 68‐kDa recombinant human DNA topoisomerase I (TopoI) in solution, in a complex with a 16‐bp DNA fragment containing a camptothecin‐enhanced TopoI cleavage site, and in a ternary complex with this oligonucleotide and topotecan. Raman spectroscopy reveals a TopoI secondary structure transition and significant changes in the hydrogen bonding of the tyrosine residues induced by the DNA binding. CD spectroscopy confirms the Raman data and identifies a DNA‐induced (>7%) decrease of the TopoI α helix accompanied by at least a 6% increase of the β structure. The Raman DNA molecular signatures demonstrated a bandshift that is expected for a net change in the environment of guanine C6O groups from pairing to solvent exposure. The formation of a ternary cleavage complex with TopoI, DNA, and topotecan as probed by CD spectroscopy reveals neither additional modifications of the TopoI secondary structure nor of the oligonucleotide structure, compared to the TopoI–oligonucleotide complex. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 67: 369–375, 2002