1i4s
From Proteopedia
| |||||||
| , resolution 2.15Å | |||||||
|---|---|---|---|---|---|---|---|
| Activity: | Ribonuclease III, with EC number 3.1.26.3 | ||||||
| Related: | 1STU, 1DI2
| ||||||
| Resources: | FirstGlance, OCA, PDBsum, RCSB | ||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
CRYSTAL STRUCTURE OF RNASE III ENDONUCLEASE DOMAIN FROM AQUIFEX AEOLICUS AT 2.15 ANGSTROM RESOLUTION
Overview
BACKGROUND: Aquifex aeolicus Ribonuclease III (Aa-RNase III) belongs to the family of Mg(2+)-dependent endonucleases that show specificity for double-stranded RNA (dsRNA). RNase III is conserved in all known bacteria and eukaryotes and has 1-2 copies of a 9-residue consensus sequence, known as the RNase III signature motif. The bacterial RNase III proteins are the simplest, consisting of two domains: an N-terminal endonuclease domain, followed by a double-stranded RNA binding domain (dsRBD). The three-dimensional structure of the dsRBD in Escherichia coli RNase III has been elucidated; no structural information is available for the endonuclease domain of any RNase III. RESULTS: We present the crystal structures of the Aa-RNase III endonuclease domain in its ligand-free form and in complex with Mn(2+). The structures reveal a novel protein fold and suggest a mechanism for dsRNA cleavage. On the basis of structural, genetic, and biological data, we have constructed a hypothetical model of Aa-RNase III in complex with dsRNA and Mg(2+) ion, which provides the first glimpse of RNase III in action. CONCLUSIONS: The functional Aa-RNase III dimer is formed via mainly hydrophobic interactions, including a "ball-and-socket" junction that ensures accurate alignment of the two monomers. The fold of the polypeptide chain and its dimerization create a valley with two compound active centers at each end of the valley. The valley can accommodate a dsRNA substrate. Mn(2+) binding has significant impact on crystal packing, intermolecular interactions, thermal stability, and the formation of two RNA-cutting sites within each compound active center.
About this Structure
1I4S is a Single protein structure of sequence from Aquifex aeolicus. Full crystallographic information is available from OCA.
Reference
Crystallographic and modeling studies of RNase III suggest a mechanism for double-stranded RNA cleavage., Blaszczyk J, Tropea JE, Bubunenko M, Routzahn KM, Waugh DS, Court DL, Ji X, Structure. 2001 Dec;9(12):1225-36. PMID:11738048
Page seeded by OCA on Sun Mar 30 21:14:39 2008
