[Molecular mechanisms of spontaneous transversions and transitions]

Molecular mechanisms of spontaneous base substitutions during template directed nucleic acid synthesis have been considered. For this purpose calculations of interaction energy in various coplanar base pairs with approximately such glycoside bond positions as for Watson--Crick base pairs have been carried out by means of atom-atom potential function method. A number of this energy local minima which could be realized in double helix during template synthesis have been found. The calculation results permit to present purine-purine pair formation with transition of one of nucleotides to syn-conformation as the main transversion pathway and formation of wobble pairs UG and AC as the transition pathway. A possible contribution of interactions between base pairs and enzyme to fidelity of template synthesis have been evaluated. Calculation results are in accord with experimental data on spontaneous mutation frequencies of errors in nucleic acid synthesis in vitro.