The DNA substrate preference comparison between RNase T, ExoI, and ExoX.

(A) The 5′-end ³²P-labelled single-stranded 11-nucleotide DNA molecules were digested with similar efficiencies by RNase T, ExoI, and ExoX. (B) RNase T is more specific than ExoX in digesting a Y-structured DNA and generated the end product with a 1-nucleotide overhang. ExoI did not digest a Y-structured DNA at low enzyme concentrations. (C) RNase T is more specific than ExoX at digesting a duplex DNA with a short overhang to generate a more specific end product of a duplex with a 1-nucleotide overhang. ExoI did not digest duplex DNA with a short overhang at low enzyme concentrations.