Guillet V, Lapthorn A, Mauguen Y
Laboratoire de Physique, CNRS, UPR180, Centre d'Etudes Pharmaceutiques, Chatenay-Malabry, France.
FEBS Lett. 1993 Sep 13;330(2):137-40. doi: 10.1016/0014-5793(93)80259-w.
Barnase has been co-crystallized at neutral pH with its natural product the 3'-guanylic acid. The X-ray structure was solved by molecular replacement methods and refined to a final R-factor of 18.7%. The protein folding is essentially the same as that of the native form. The base recognition site is almost identical to that of the homologous binase-3'GMP complex, but the nucleotide is bound in a productive binding mode for a substrate with a syn glycosyl torsion angle allowing the general base Glu73 to hydrogen bond with the 2'O of the nucleotide as is assumed in the classical catalytic mechanism. The two molecules of the asymmetric unit form a dimer and the positions of the two nucleotides partially mimic the interaction of the RNA with the enzyme, one of the inhibitors being located in a secondary subsite.
芽孢杆菌RNA酶已在中性pH条件下与其天然产物3'-鸟苷酸共结晶。通过分子置换法解析了X射线结构，并将其精修至最终R因子为18.7%。蛋白质折叠与天然形式基本相同。碱基识别位点与同源的双酶-3'GMP复合物几乎相同，但核苷酸以一种对底物有效的结合模式结合，具有顺式糖基扭转角，使得通用碱基Glu73能够与核苷酸的2'-O形成氢键，这与经典催化机制中的假设一致。不对称单元的两个分子形成二聚体，两个核苷酸的位置部分模拟了RNA与酶的相互作用，其中一种抑制剂位于二级亚位点。
