3U3G: Structure Of Lc11-Rnase H1 Isolated From Compost By Metagenomic Approach: Insight Into The Structural Bases For Unusual Enzymatic Properties Of Sto-Rnase H1

Metagenome-derived LC11-RNase H1 is a homolog of Sulfolobus tokodaii RNase H1 (Sto-RNase H1). It lacks a C-terminal tail, which is responsible for hyperstabilization of Sto-RNase H1. Sto-RNase H1 is characterized by its ability to cleave not only an RNA/DNA hybrid but also a double-stranded RNA (dsRNA). To examine whether LC11-RNase H1 also exhibits both RNase H and dsRNase activities, LC11-RNase H1 was overproduced in Escherichia coli, purified, and characterized. LC11-RNase H1 exhibited RNase H activity with similar metal ion preference, optimum pH, and cleavage mode of substrate with those of Sto-RNase H1. However, LC11-RNase H1 did not exhibit dsRNase activity at any condition examined. LC11-RNase H1 was less stable than Sto-RNases H1 and its derivative lacking the C-terminal tail (Sto-RNase H1DeltaC6) by 37 and 13 degrees C in T(m) , respectively. To understand the structural bases for these differences, the crystal structure of LC11-RNase H1 was determined at 1.4 A resolution. The LC11-RNase H1 structure is highly similar to the Sto-RNase H1 structure. However, LC11-RNase H1 has two grooves on protein surface, one containing the active site and the other containing DNA-phosphate binding pocket, while Sto-RNase H1 has one groove containing the active site. In addition, LC11-RNase H1 contains more cavities and buried charged residues than Sto-RNase H1. We propose that LC11-RNase H1 does not exhibit dsRNase activity because dsRNA cannot fit to the two grooves on protein surface and that LC11-RNase H1 is less stable than Sto-RNase H1DeltaC6 because of the increase in cavity volume and number of buried charged residues.
PDB ID: 3U3GDownload
MMDB ID: 97788
PDB Deposition Date: 2011/10/5
Updated in MMDB: 2012/06
Experimental Method:
x-ray diffraction
Resolution: 1.4  Å
Source Organism:
Similar Structures:
Biological Unit for 3U3G: monomeric; determined by author and by software (PISA)
Molecular Components in 3U3G
Label Count Molecule
Protein (1 molecule)
Ribonuclease H
Molecule annotation
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