INFLUENCE OF A SINGLE MODIFICATION OF THE DNA SUGAR-PHOSPHATE BACKBONE ON THE FUNCTIONING OF RESTRICTION ENDONUCLEASES ECORII, MVAI, AND BSTN1

Oligonucleotide duplexes containing modified nucleoside residues 1-(2' -deoxy-B-D-threo-pentofuranosyl)thymine (xT) or 1-(3'-deoxy-B-D-threo- pentofuranosyl)uracil (tU) in the center of the recognition site for E coRII, MvaI, and BstN1 (CCA/(T)GG) were constructed and examined in re spect of their physicochemical and substrate properties. The restricti on endonucleases proved to differ in their sensitivity to the resultin g conformational distortions. For the first time with EcoRII, the xT-c ontaining analog turned out to be a much better substrate and, moreove r, an activator of the enzyme.