Three-dimensional structure of ribonuclease H from E. coli

THE three-dimensional structure of RNase H from Escherichia coli was determined at 1.8 Å resolution by X-ray crystallography. The enzyme was found to belong to the α + β class of structures, consisting of two distinct domains. The structure implies a possible region interacting with a DNA-RNA hybrid. The Mg²⁺-binding site essential for activity is located near a cluster of four acidic amino acids- one glutamic and three aspartic acid residues. These residues are completely conserved in the homology alignment of sequences of RNase H and reverse transcriptases from retro viruses and retrovirus-like entities^1,2. The structural motif of β strands around the Mg²⁺-binding site has similarities to that in DNase I^3-6.