A "moving metal mechanism" for substrate cleavage by the DNA repair endonuclease APE-1.
Apurinic/apyrimidinic endonuclease (APE-1) is essential for base excision repair (BER) of damaged DNA. Here molecular dynamics (MD) simulations of APE1 complexed with cleaved and uncleaved damaged DNA were used to determine the role and position of the metal ion(s) in the active site before and after DNA cleavage. The simulations started from an energy minimized wild-type structure of the metal-free APE1/damaged-DNA complex (1DE8). A grid search with one Mg2+ ion located two low energy clusters of Mg2+ consistent with the experimentally determined metal ion positions. At the start of the longer MD simulations, Mg2+ ions were placed at different positions as seen in the crystal structures and the movement of the ion was followed over the course of the trajectory. Our analysis suggests a "moving metal mechanism" in which one Mg2+ ion moves from the B- (more buried) to the A-site during substrate cleavage. The anticipated inversion of the phosphate oxygens occurs during the in-line cleavage reaction. Experimental results, which show competition between Ca2+ and Mg2+ for catalyzing the reaction, and high concentrations of Mg2+ are inhibitory, indicate that both sites cannot be simultaneously occupied for maximal activity.
Oezguen
Numan
N
Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas 77555-0857, USA.
Schein
Catherine H
CH
Peddi
Srinivasa R
SR
Power
Trevor D
TD
Izumi
Tadahide
T
Braun
Werner
W
D003198:Computer Simulation; D004247:DNA / Q000378:metabolism*; D004260:DNA Repair; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008274:Magnesium / Q000378:metabolism*; D008958:Models, Molecular
D004247:DNA; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D008274:Magnesium