title: Noncatalytic assembly of ribonuclease III with double-stranded RNA.
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.
authors.affiliation: Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, MD 21702 USA.
authors.forename: Jaroslaw
authors.initials: J
authors.lastname: Blaszczyk
authors.forename: Jianhua
authors.initials: J
authors.lastname: Gan
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Tropea
authors.forename: Donald L
authors.initials: DL
authors.lastname: Court
authors.forename: David S
authors.initials: DS
authors.lastname: Waugh
authors.forename: Xinhua
authors.initials: X
authors.lastname: Ji
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D008274:Magnesium / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D012330:RNA, Double-Stranded / Q000378:metabolism*; D043244:Ribonuclease III / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D012330:RNA, Double-Stranded; D043244:Ribonuclease III; D008274:Magnesium