Effect of the termini of RNase Hs from <italic>Chlamydophila pneumoniae</italic> on enzymatic biochemical characterization

Abstract

A difference between prokaryotic RNase HII and HIII, which both belong to type 2 RNase H, is a long N-terminal extension of HIII; however, the main-fold structures of HII and HIII known as RNase H-fold are similar. D). Moreover, IIC19D IIIN 82 -88 mutant, prepared through adding N-terminal 82nd to 88th residues locating at the bound region of N-and C-terminal domains of CpRNase HIII to N-terminus of IIC19 D , cleaved DR 4 D substrate more efficiently and preferentially at the cleavage sites of CpRNase HIII but not those of CpRNase HII. These results indicated that C-termini of CpRNase HII, N-termini of CpRNase HIII, and bound region of N-and C-terminal domain are all important for enzymatic activities. Moreover, the 82nd to 88th residues of N-terminus of CpRNase HII are related with enzyme cleavage site specificity. These results will help to understand the importance of C-termini of CpRNase HII and N-termini of CpRNase HIII to the enzyme activities for DR 1 D and DR 4 D substrate.

The catalytic mechanism, metal dependence, substrate specificity, and biodiversity of ribonuclease H

“…These findings demonstrate that the tyrosine residue conserved in RNases HII may not be the only way for RNases H to bind the single ribose in DNA-rN 1 -DNA/DNA substrates, as there is no such a tyrosine in RNases HIII. A serine residue in C. pneumoniae RNase HIII is involved in the recognition of the single ribose in dsDNA ( Lu et al, 2012a ; Hou et al, 2012b ), but this residue does not seem to be conserved among HIIIs. The mechanism underlying the cleavage of RNase HIII on dsDNA containing a single ribose is therefore still unclear.…”