Substrate properties of C'-methyl UTP derivatives in T7 RNA polymerase reactions. Evidence for N-type NTP...

The number of synthetic UTP analogues containing methyl groups in different positions of the ribose moiety were tested as substrates for T7 RNA polymerase (T7 RNAP). Two of these compounds (containing substituents in the 5' position) were shown to be weak substrates of T7 RNAP. 3'Me-UTP was neither substrate nor inhibitor of T7 RNAP while 2'Me-UTP was shown to terminate RNA chain synthesis. Conformational analysis of the analogues and parent nucleotide using the force-field method indicates that the allowed conformation of UTP during its incorporation into the growing RNA chain by T7 RNAP is limited to the chi angle range of 192-256 degrees of N-type conformation.