[DNA polymerase I, Klenow fragment of Escherichia coli: hydrolysis and pyrophosphorolysis of DNA containing phosphothioate groups].

Reaction of DNA synthesis catalyzed by DNA polymerase I KF in the presence of 2'-deoxynucleoside 5'-alpha-thiotriphosphates (dNTP alpha S) was investigated. DNA with thiophosphate groups (DNA[P=S]) obtained by such a way was studied in reactions of hydrolysis and pyrophosphorolysis catalyzed by DNA polymerase I KF. It is shown that the rate of DNA elongation is decreased both on the step of incorporation of dNMP alpha S residues and on the step of incorporation of the next dNMP residue. The rate of pyrophosphorolysis of 3'-terminal dNMP alpha S was demonstrated to be one order of magnitude less in comparison with the corresponding reaction with the natural dNMP residue. Contrary, the rate of 3'----5'-exonuclease hydrolysis of both DNA[P=S] and DNA of the same structure revealed no distinguishable differences.