Department of Biochemistry and Biocenter Oulu, University of Oulu, Oulu, Finland.
PLoS One. 2012;7(2):e32336. doi: 10.1371/journal.pone.0032336. Epub 2012 Feb 29.
The 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) is a highly abundant membrane-associated enzyme in the myelin sheath of the vertebrate nervous system. CNPase is a member of the 2H phosphoesterase family and catalyzes the formation of 2'-nucleotide products from 2',3'-cyclic substrates; however, its physiological substrate and function remain unknown. It is likely that CNPase participates in RNA metabolism in the myelinating cell. We solved crystal structures of the phosphodiesterase domain of mouse CNPase, showing the binding mode of nucleotide ligands in the active site. The binding mode of the product 2'-AMP provides a detailed view of the reaction mechanism. Comparisons of CNPase crystal structures highlight flexible loops, which could play roles in substrate recognition; large differences in the active-site vicinity are observed when comparing more distant members of the 2H family. We also studied the full-length CNPase, showing its N-terminal domain is involved in RNA binding and dimerization. Our results provide a detailed picture of the CNPase active site during its catalytic cycle, and suggest a specific function for the previously uncharacterized N-terminal domain.
2',3'-环核苷酸 3'-磷酸二酯酶（CNPase）是脊椎动物神经系统髓鞘中高度丰富的膜相关酶。CNPase 是 2H 磷酸酯酶家族的成员，催化 2'，3'-环底物形成 2'-核苷酸产物；然而，其生理底物和功能仍然未知。CNPase 可能参与髓鞘形成细胞中的 RNA 代谢。我们解决了鼠 CNPase 的磷酸二酯酶结构域的晶体结构，显示了活性位点中核苷酸配体的结合模式。产物 2'-AMP 的结合模式提供了反应机制的详细视图。CNPase 晶体结构的比较突出了灵活的环，这些环可能在底物识别中发挥作用；当比较 2H 家族中更远的成员时，在活性位点附近观察到了较大的差异。我们还研究了全长 CNPase，表明其 N 端结构域参与 RNA 结合和二聚化。我们的结果提供了 CNPase 催化循环中活性位点的详细图片，并为以前未表征的 N 端结构域提供了特定的功能。
