Fig. 5.

RNase H1 cleaves the RNA strand in an RNA/DNA hybrid. (A) A diagram of RNase H1 (green oval) bound to RNA/DNA hybrid (DNA in light yellow, RNA in orange). The scissile phosphate is in the active site (red atoms), and two divalent atoms A and B mediate the interactions between the DEDD catalytic residues of RNase H1 and RNA substrate. (B) RNase H1 is a sequence non-specific ribonuclease and may “slide” on its substrates, which leads to binding with different registers in crystal forms. Dark and light green symbols represent two alternative binding modes of Bh-RNase H1 on a 12 bp RNA/DNA hybrid.