2DCH: Crystal Structure Of Archaeal Intron-Encoded Homing Endonuclease I- Tsp061i

A novel LAGLIDADG-type homing endonuclease (HEase), I-Tsp061I, from the hyperthermophilic archaeon Thermoproteus sp. IC-061 16 S rRNA gene (rDNA) intron was characterized with respect to its structure, catalytic properties and thermostability. It was found that I-Tsp061I is a HEase isoschizomer of the previously described I-PogI and exhibits the highest thermostability among the known LAGLIDADG-type HEases. Determination of the crystal structure of I-Tsp061I at 2.1 A resolution using the multiple isomorphous replacement and anomalous scattering method revealed that the overall fold is similar to that of other known LAGLIDADG-type HEases, despite little sequence similarity between I-Tsp061I and those HEases. However, I-Tsp061I contains important cross-domain polar networks, unlike its mesophilic counterparts. Notably, the polar network Tyr6-Asp104-His180-107O-HOH12-104O-Asn177 exists across the two packed alpha-helices containing both the LAGLIDADG catalytic motif and the GxxxG hydrophobic helix bundle motif. Another important structural feature is the salt-bridge network Asp29-Arg31-Glu182 across N and C-terminal domain interface, which appears to contribute to the stability of the domain/domain packing. On the basis of these structural analyses and extensive mutational studies, we conclude that such cross-domain polar networks play key roles in stabilizing the catalytic center and domain packing, and underlie the hyperthermostability of I-Tsp061I.
PDB ID: 2DCHDownload
MMDB ID: 40348
PDB Deposition Date: 2006/1/6
Updated in MMDB: 2011/11
Experimental Method:
x-ray diffraction
Resolution: 2.06  Å
Source Organism:
Similar Structures:
Biological Unit for 2DCH: monomeric; determined by author
Molecular Components in 2DCH
Label Count Molecule
Protein (1 molecule)
Putative Homing Endonuclease
Molecule annotation
Chemicals (3 molecules)
* Click molecule labels to explore molecular sequence information.

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