... doi:10.1046/j.1432-1033.2002.02837.x In addition, the protrusion of the U towards the minorgroove side of the hairpin stem may also lead to sterichindrance in the approach of UDG to DNA. On the otherhand, U15 in the U4-hairpin, ... U4-hairpin, the best substrate of the four, islocated in an environment wherein both the backbone and the base conformation mimic the B-form of DNA. Thus the structural features of the U2-hairpin ... comparison of the three-dimensional structures of U2- and U4-hairpins revealed that the stretched-out backbone conformation in the vicinity of U13 in the U2-hairpin [4,5] is the reason for the enzyme...