The role of mismatched nucleotides in activating the hMSH2-hMSH6 molecular switch

J Biol Chem. 2000 Feb 11;275(6):3922-30. doi: 10.1074/jbc.275.6.3922.


We have previously shown that hMSH2-hMSH6 contains an intrinsic ATPase which is activated by mismatch-provoked ADP-->ATP exchange that coordinately induces the formation of a sliding clamp capable of hydrolysis-independent diffusion along the DNA backbone (1,2). These studies suggested that mismatch repair could be propagated by a signaling event transduced via diffusion of ATP-bound hMSH2-hMSH6 molecular switches to the DNA repair machinery. The Molecular Switch model (Fishel, R. (1998) Genes Dev. 12, 2096-2101) is considerably different than the Hydrolysis-Driven Translocation model (Blackwell, L. J., Martik, D., Bjornson, K. P., Bjornson, E. S., and Modrich, P. (1998) J. Biol. Chem. 273, 32055-32062) and makes additional testable predictions beyond the demonstration of hydrolysis-independent diffusion (Gradia, S., Subramanian, D., Wilson, T., Acharya, S., Makhov, A., Griffith, J., and Fishel, R. (1999) Mol. Cell 3, 255-261): (i) individual mismatch-provoked ADP-->ATP exchange should be unique and rate-limiting, and (ii) the k(cat x DNA) for the DNA-stimulated ATPase activity should decrease with increasing chain length. Here we have examined hMSH2-hMSH6 affinity and ATPase stimulatory activity for several DNA substrates containing mispaired nucleotides as well as the chain length dependence of a defined mismatch under physiological conditions. We find that the results are most consistent with the predictions of the Molecular Switch model.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Diphosphate / metabolism
  • Adenosine Triphosphatases / metabolism
  • Adenosine Triphosphate / metabolism
  • Base Pair Mismatch
  • Binding, Competitive
  • DNA / pharmacology
  • DNA Repair / genetics*
  • DNA-Binding Proteins / metabolism*
  • Dimerization
  • Enzyme Activation
  • Humans
  • Kinetics
  • MutS Homolog 2 Protein
  • Oligodeoxyribonucleotides / metabolism
  • Oligodeoxyribonucleotides / pharmacology
  • Proto-Oncogene Proteins / metabolism*
  • Salts / pharmacology


  • DNA-Binding Proteins
  • G-T mismatch-binding protein
  • Oligodeoxyribonucleotides
  • Proto-Oncogene Proteins
  • Salts
  • Adenosine Diphosphate
  • Adenosine Triphosphate
  • DNA
  • Adenosine Triphosphatases
  • MSH2 protein, human
  • MutS Homolog 2 Protein