title: Solution structure and base specificity of cytotoxic RC-RNase 2 from Rana catesbeiana.
abstract: Cytotoxic ribonucleases found in the oocytes and early embryos of frogs with antitumor activity are well-documented. RC-RNase 2, a cytotoxic ribonuclease isolated from oocytes of bullfrog Rana catesbeiana, consists of 105 residues linked with 4 disulfide bridges and belongs to the bovine pancreatic ribonuclease (RNase A) superfamily. Among the RC-RNases, the base preference for RNase 2 is UpG but CpG for RC-RNase 4; while RC-RNase possesses the base specificity of both UpG and CpG. Interestingly, RC-RNase 2 or 4 has much lower catalytic activity but only three-fold less cytotoxicity than RC-RNase. Here, we report the NMR solution structure of rRC-RNase 2, comprising three alpha-helices and two sets of antiparallel beta-sheets. The differences of side-chain conformations of subsite residues among RNase A, RC-RNase, RC-RNase 4 and rRNase 2 are related to their distinct catalytic activities and base preferences. Furthermore, the substrate-related residues in the base specificity among native RC-RNases are derived using the chemical shift perturbation on ligand binding.
authors: Department of Agricultural Chemistry, National Taiwan University, Taipei 10617, Taiwan; Genome and Systems Biology Degree Program, Center for Systems Biology, National Taiwan University, Taipei 10617, Taiwan. Electronic address: andyhsu@ntu.edu.tw.
authors: Chun-Hua
authors: CH
authors: Hsu
authors: Genomics Research Center, Academia Sinica, Taipei 11529, Taiwan.
authors: Chi-Fon
authors: CF
authors: Chang
authors: Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan.
authors: You-Di
authors: YD
authors: Liao
authors: Institute of Biological Chemistry, Academia Sinica, Taipei 11529, Taiwan.
authors: Shih-Hsiung
authors: SH
authors: Wu
authors: Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan. Electronic address: bmchinp@ibms.sinica.edu.tw.
authors: Chinpan
authors: C
authors: Chen
mesh_terms: D029845:Amphibian Proteins / Q000737:chemistry*; D000818:Animals; D002417:Cattle; D004722:Endoribonucleases / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D009865:Oocytes / Q000201:enzymology; D017433:Protein Structure, Secondary; D011892:Rana catesbeiana
chemical_list: D029845:Amphibian Proteins; D004722:Endoribonucleases; C029494:ribonuclease U
keywords: Base specificity; NMR; RC-RNase 2; Ribonuclease; Solution structure