PDBsum entry 3if0

Hydrolase

PDB id: 3if0

Contents

Protein chain

149 a.a. *

* Residue conservation analysis

PDB id:

3if0

Name:

Hydrolase

Title:

Crystal structure of the nanoarchaeum equitans tRNA splicing endonuclease structural subunit

Structure:

Neq261. Chain: x. Engineered: yes

Source:

Nanoarchaeum equitans. Organism_taxid: 160232. Gene: neq261. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

2.20Å R-factor: 0.250 R-free: 0.277

Authors:

M.Mitchell,H.Li

Key ref:

M.Mitchell et al. (2009). Crystal structure and assembly of the functional Nanoarchaeum equitans tRNA splicing endonuclease. Nucleic Acids Res, 37, 5793-5802. PubMed id: 19578064

Date:

23-Jul-09 Release date: 18-Aug-09

Protein chain

Q74MS9  (Q74MS9_NANEQ) -  NEQ261 from Nanoarchaeum equitans (strain Kin4-M)

Seq: 153 a.a.

Struc: 149 a.a.

Nucleic Acids Res 37:5793-5802 (2009)

PubMed id: 19578064

Crystal structure and assembly of the functional Nanoarchaeum equitans tRNA splicing endonuclease.

M.Mitchell, S.Xue, R.Erdman, L.Randau, D.Söll, H.Li.

ABSTRACT

The RNA splicing and processing endonuclease from Nanoarchaeum equitans (NEQ) belongs to the recently identified (alphabeta)(2) family of splicing endonucleases that require two different subunits for splicing activity. N. equitans splicing endonuclease comprises the catalytic subunit (NEQ205) and the structural subunit (NEQ261). Here, we report the crystal structure of the functional NEQ enzyme at 2.1 A containing both subunits, as well as that of the NEQ261 subunit alone at 2.2 A. The functional enzyme resembles previously known alpha(2) and alpha(4) endonucleases but forms a heterotetramer: a dimer of two heterodimers of the catalytic subunit (NEQ205) and the structural subunit (NEQ261). Surprisingly, NEQ261 alone forms a homodimer, similar to the previously known homodimer of the catalytic subunit. The homodimers of isolated subunits are inhibitory to heterodimerization as illustrated by a covalently linked catalytic homodimer that had no RNA cleavage activity upon mixing with the structural subunit. Detailed structural comparison reveals a more favorable hetero- than homodimerization interface, thereby suggesting a possible regulation mechanism of enzyme assembly through available subunits. Finally, the uniquely flexible active site of the NEQ endonuclease provides a possible explanation for its broader substrate specificity.