DNA polymerase I (Klenow fragment): Role of the structure and length of a template in enzyme recognition

Abstract
The values of K d and Gibbs energy (ΔG°) have been measured for complexes of the template site of DNA polymerase I Klenow fragment with the homo‐oligonucleotides d(pC) n , d(pT) n , d(pG) n and d(pA) n and hetero‐oligonucleotides of various structures and lengths. These parameters were evaluated from the protective effect of the oligonucleotide on enzyme inactivation by the affinity reagents d(Tp)2C[Pt2+(NH3)2OH](pT)7 and d[(Tp)2C(Pt2+(NH3)2OH)p]3T of the template site. The present results and previously reported data [(1985) Biorg. Khim. 13, 357–369] indicate that the nucleoside components of the template form complexes as a result of their hydrophobic interactions with the enzyme. Only one template internucleotide phosphate forms an Me2+‐dependent electrostatic contact and a hydrogen bond with the enzyme. The 19–20‐nucleotide fragments of the template appear to interact with the protein molecule.