Noncatalytic Assembly of Ribonuclease III with Double-Stranded RNA.
Blaszczyk, J., Gan, J., Tropea, J.E., Court, D.L., Waugh, D.S., Ji, X.(2004) Structure 12: 457-466
- PubMed: 15016361 
- DOI: https://doi.org/10.1016/j.str.2004.02.004
- Primary Citation of Related Structures:  
1RC5, 1RC7 - PubMed Abstract: 
Ribonuclease III (RNase III) represents a family of double-stranded RNA (dsRNA) endonucleases. The simplest bacterial enzyme contains an endonuclease domain (endoND) and a dsRNA binding domain (dsRBD). RNase III can affect RNA structure and gene expression in either of two ways: as a dsRNA-processing enzyme that cleaves dsRNA, or as a dsRNA binding protein that binds but does not cleave dsRNA. We previously determined the endoND structure of Aquifex aeolicus RNase III (Aa-RNase III) and modeled a catalytic complex of full-length Aa-RNase III with dsRNA. Here, we present the crystal structure of Aa-RNase III in complex with dsRNA, revealing a noncatalytic assembly. The major differences between the two functional forms of RNase III.dsRNA are the conformation of the protein and the orientation and location of dsRNA. The flexibility of a 7 residue linker between the endoND and dsRBD enables the transition between these two forms.
Organizational Affiliation: 
Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, MD 21702 USA.