specific contacts between the escherichia coli rna polymerase ( nucleosidetriphosphate : rna nucleotidyl-transferase , ec2.7.7.6 ) and the phosphates and purine bases of the a3 promoter of phage t7 cluster into three regions located approximately 10 , 16 , and 35 base pairs before rna initiation site .
C0035681
rna polymerase
C0035673
rna nucleotidyl-transferase