The pH dependent configurations of the C.A mispair in DNA.

AUTOR(ES)

Boulard, Y

RESUMO

The structure of the cytosine-adenine mispair in a 7 base pair duplex has been investigated by proton NMR spectroscopy. At low pH, the predominant structure is protonated on the A residue and assumes a wobble conformation consistent with previous findings. The C residue of the mispair is found in a C2'-C3' endo equilibrium. This is confirmed by molecular dynamics calculations which suggest that the conformation of the protonated wobble is flexible and not as rigid as a normal base pair. As the solution pH is raised, a structural transition is observed with an apparent pK of 7.54 at 23 degrees C. At higher pH the predominant structure is one in which both the C and A residues are intrahelical. Evidence is presented that this structure corresponds to a reverse wobble in which the two bases are held together by one hydrogen bond. This structure is much less stable than the protonated form and even at low temperature single strands are observed in slow exchange with the neutral duplex form.

Documentos Relacionados

• pH-dependent specific binding and combing of DNA.
• Reorientations in the bacteriorhodopsin photoscycle are pH dependent.
• The alkaline pH dependence of chymotrypsin reactions: postulation of a pH-dependent intramolecular competitive inhibition.
• Eosinophil viability is increased by acidic pH in a cAMP- and GPR65-dependent manner
• Ca2+ Regulates Reactive Oxygen Species Production and pH during Mechanosensing in Arabidopsis Roots[C][W]