Centre Armand-Frappier Santé Biotechnologie , Institut National de la Recherche Scientifique (INRS), Université du Québec , 531 Boulevard des Prairies , Laval , Quebec City H7V 1B7 , Canada.
Genome Science and Technology , University of Tennesse , Knoxville , Tennessee 37996 , United States.
Biochemistry. 2020 Feb 18;59(6):755-765. doi: 10.1021/acs.biochem.9b00888. Epub 2020 Jan 24.
Ribonuclease 6 (RNase 6) is one of eight catalytically active human pancreatic-type RNases that belong to a superfamily of rapidly evolving enzymes. Like some of its human homologues, RNase 6 exhibits host defense properties such as antiviral and antibacterial activities. Recently solved crystal structures of this enzyme in its nucleotide-free form show the conservation of the prototypical kidney-shaped fold preserved among vertebrate RNases, in addition to revealing the presence of a unique secondary active site. In this study, we determine the structural and conformational properties experienced by RNase 6 upon binding to substrate and product analogues. We present the first crystal structures of RNase 6 bound to a nucleotide ligand (adenosine 5'-monophosphate), in addition to RNase 6 bound to phosphate ions. While the enzyme preserves B subsite ligand preferences, our results show a lack of typical B subsite interactions normally observed in homologous ligand-bound RNases. A comparison of the dynamical properties of RNase 6 in its apo-, substrate-, and product-bound states highlight the unique dynamical properties experienced on time scales ranging from nano- to milliseconds. Overall, our results confirm the specific evolutionary adaptation of RNase 6 relative to its unique catalytic and biological activities.
核糖核酸酶 6（RNase 6）是八种具有催化活性的人类胰腺型核糖核酸酶之一，属于快速进化酶的超家族。像其一些人类同源物一样，RNase 6 具有宿主防御特性，如抗病毒和抗菌活性。最近解决的这种酶在无核苷酸形式下的晶体结构表明，除了揭示存在独特的次级活性位点外，保留了脊椎动物核糖核酸酶之间保存的原型肾形折叠的保守性。在这项研究中，我们确定了 RNase 6 在与底物和产物类似物结合时经历的结构和构象特性。我们首次展示了与核苷酸配体（腺苷 5'-单磷酸）结合的 RNase 6 的晶体结构，以及与磷酸离子结合的 RNase 6。虽然该酶保留了 B 亚基配体偏好，但我们的结果表明，在同源配体结合的核糖核酸酶中通常观察到的典型 B 亚基相互作用缺失。对 RNase 6 在无配体、底物和产物结合状态下的动态特性进行比较，突出了在纳秒到毫秒时间尺度上经历的独特动态特性。总体而言，我们的结果证实了 RNase 6 相对于其独特的催化和生物学活性的特定进化适应。
