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Crystal Structure of MN(II)-Complex of RNAse III Endonuclease Domain from Aquifex Aeolicus at 2.10 Angstrom Resolution
Structural highlights
FunctionRNC_AQUAE Digests double-stranded RNA. Involved in the processing of primary rRNA transcript to yield the immediate precursors to the large and small rRNAs (23S and 16S). Also processes some mRNAs, and tRNAs when they are encoded in the rRNA operon.[1] [2] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedBACKGROUND: 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. 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[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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