Pletnev V Z, Tsygannik I N, Mikhaĭlova I Iu, Ivanov V T, Lengs D A, Grokhul'skiĭ P, Diuéks V L
Bioorg Khim. 1991 Mar;17(3):359-71.
The crystal structure of a synthetic analogue of meso-valinomycin, crystallized with two acetone molecules, has been solved by X-ray direct methods. The trigonal crystals belong to the P32 space group, with the number of molecules in the unit cell z = 3, and cell dimensions a = b = 15,2085 A, c = 29,3250 A, alpha = beta = 90 degrees, gamma = 120 degrees. The standard (R) and weighted (Rw) factors after the structure refinement of atoms C, N, O in anisotropic thermal motion approximation and with the contribution from H atoms taken into account are 0,070 and 0,082, respectively. The molecule adopts an asymmetric conformations stabilized by six amide intramolecular hydrogen bonds NH ... OC of the 4----4 type; one of those is strong and the other are weakened in different extent. The side chains occupy the external pseudoaxial positions towards the cyclic frame of the molecule, whereas six free ester carbonyl groups have different orientations. In contrast to meso-valinomycin, the analogue under study has no specific binding site for metal ions. The isopropyl side chains of D-Hyi(2) and Hyi(4) residues effectively shield, from both sides, the access to the inner molecular cavity.
已通过X射线直接法解析了与两个丙酮分子一起结晶的内消旋缬氨霉素合成类似物的晶体结构。三方晶体属于P32空间群，晶胞中的分子数z = 3，晶胞参数a = b = 15.2085 Å，c = 29.3250 Å，α = β = 90°，γ = 120°。在各向异性热运动近似下对原子C、N、O进行结构精修并考虑H原子贡献后，标准（R）因子和加权（Rw）因子分别为0.070和0.082。该分子采用由六个4----4型酰胺分子内氢键NH...OC稳定的不对称构象；其中一个氢键较强，其他氢键在不同程度上减弱。侧链朝向分子的环状骨架占据外部假轴向位置，而六个游离酯羰基具有不同的取向。与内消旋缬氨霉素不同，所研究的类似物没有金属离子的特异性结合位点。D-Hyi(2)和Hyi(4)残基的异丙基侧链从两侧有效地屏蔽了进入分子内腔的通道。
