Ribonuclease H (RNase H) type II family (prokaryotic RNase HII and HIII, and eukaryotic RNase H2/HII)
This family contains ribonucleases HII (RNases H2) which include bacterial RNase HII and HIII, and eukaryotic and archaeal RNase H2/HII. RNase H2 cleaves RNA sequences that are part of RNA/DNA hybrids or that are incorporated into DNA, thereby preventing genomic instability and the accumulation of aberrant nucleic acid which can induce Aicardi-Goutieres syndrome, a severe autoimmune disorder in humans. Ribonuclease H (RNase H) is classified into two families, type I (prokaryotic RNase HI, eukaryotic RNase H1 and viral RNase H) and type II (prokaryotic RNase HII and HIII, and eukaryotic RNase H2/HII). RNase H endonucleolytically hydrolyzes an RNA strand when it is annealed to a complementary DNA strand in the presence of divalent cations. The enzyme can be found in bacteria, archaea, and eukaryotes. Most prokaryotic and eukaryotic genomes contain multiple RNase H genes, but no prokaryotic genome contains the combination of only RNase HI and HIII. Despite a lack of evidence for homology from sequence comparisons, type I and type II RNase H share a common fold and similar steric configurations of the four acidic active-site residues, suggesting identical or very similar catalytic mechanisms. It appears that type I and type II RNases H also have overlapping functions in cells, as over-expression of Escherichia coli RNase HII can complement an RNase HI deletion phenotype in E. coli.
Structure:2ETJ; Thermotoga maritima RNase HII binds magnesium ion; contacts at 4.5A
Structure:1I3A; Archaeglobus fulgidus RNase HII binds cobalt(III)-hexammine chloride, demonstrating coordination of a divalent metal ion; contacts at 4A.
Jiyao W et al.(2023). "The conserved domain database in 2023.",