Catalytic center of an archaeal type 2 ribonuclease H as revealed by X-ray crystallographic and mutational analyses.
The catalytic center of an archaeal Type 2 RNase H has been identified by a combination of X-ray crystallographic and mutational analyses. The crystal structure of the Type 2 RNase H from Thermococcus kodakaraensis KOD1 has revealed that the N-terminal major domain adopts the RNase H fold, despite the poor sequence similarity to the Type 1 RNase H. Mutational analyses showed that the catalytic reaction requires four acidic residues, which are well conserved in the Type 1 RNase H and the members of the polynucleotidyl transferase family. Thus, the Type 1 and Type 2 RNases H seem to share a common catalytic mechanism, except for the requirement of histidine as a general base in the former enzyme. Combined with the results from deletion mutant analyses, the structure suggests that the C-terminal domain of the Type 2 RNase H is involved in the interaction with the DNA/RNA hybrid.
Department of Material and Life Science, Graduate School of Engineering, Osaka University, Osaka 565-0871, Japan.
A
A
Muroya
D
D
Tsuchiya
M
M
Ishikawa
M
M
Haruki
M
M
Morikawa
S
S
Kanaya
K
K
Morikawa
D001105:Archaea / Q000201:enzymology; D020134:Catalytic Domain / Q000502:physiology*; D018360:Crystallography, X-Ray / Q000295:instrumentation / Q000379:methods*; D004926:Escherichia coli / Q000235:genetics; D007527:Isoenzymes / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed / Q000235:genetics*; D009713:Nucleotidyltransferases / Q000737:chemistry; D016914:Ribonuclease H / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D013379:Substrate Specificity / Q000502:physiology; D019712:Thermococcus / Q000201:enzymology*
D007527:Isoenzymes; D009713:Nucleotidyltransferases; D016914:Ribonuclease H