We have designed a hammerhead-type RNA system which consists of three RNA fagments for normal and modified complexes which contain a non-cleavable substrate with 2'-O-methylcytidine and a guanosine-to-inosine replaced enzyme. Examination of the RNA-cleaving activity and conformational properties of the complexes suggests that the 2-amino group of a conserved guanosine residue in the loop region plays an important role for maintaining both the activity and loop conformation.
