RECOGNITION OF 2'-HYDROXYL GROUPS BY ESCHERICHIA-COLI RIBONUCLEASE HI

In order to investigate the hydrogen-bonding interactions between Esch erichia coli ribonuclease HI and the 2'-hydroxyl functions of the subs trate, oligonucleotide duplexes containing 2'-amino-2'-deoxyuridine or 2'-fluoro-2'-deoxyuridine at a specific site were used, and their aff inities for the enzyme were determined by kinetic analyses. The result s indicate that the hydroxyl groups of the nucleoside 3'-adjacent to t he cleaved phosphodiester linkage and the second nucleoside 5' to the cleaved phosphodiester act as both a proton donor and an acceptor and as a proton acceptor, respectively, in the enzyme-substrate complex. A molecular model was constructed using the interactions derived from t he results.