Noncatalytic Assembly of Ribonuclease III with Double-Stranded RNA

• Published in: Structure (London) 2004-03, Vol.12 (3), p.457-466
• Main Authors: Blaszczyk, Jaroslaw, Gan, Jianhua, Tropea, Joseph E, Court, Donald L, Waugh, David S, Ji, Xinhua
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Aquifex aeolicus; Binding Sites; Magnesium - metabolism; Models, Molecular; Molecular Sequence Data; Mutation; Protein Structure, Quaternary; Protein Structure, Tertiary; Ribonuclease III - chemistry; Ribonuclease III - genetics; Ribonuclease III - metabolism; RNA, Double-Stranded - metabolism
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/j.str.2004.02.004

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.