Pletnev V Z, Ruzeinikov S N, Tsigannik I N, Ivanov V T, Pletnev S V, Langs D A, Duax W L
Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia.
Biopolymers. 1997 Nov;42(6):651-8. doi: 10.1002/(SICI)1097-0282(199711)42:6<651::AID-BIP4>3.0.CO;2-T.
The crystal and molecular structure of the valinomycin analogue, cyclo[(D-Val-L-Lac-L-Ala-D-Hyi)2(D-Val-L-Lac-L-Val-D-Hyi)] has been solved by x-ray direct methods using the "Shake and Bake" procedure. The crystals, grown from a mixture of octane/CH2Cl2, belong to space group P2(1) (Z = 4) with cell parameters a = 10.29, b = 32.08, c = 18.73 A, beta = 97.05 degrees, and contain two molecules per asymmetric unit. After anisotropic refinement the standard reliability factor was Rl = 0.058. The conformations of both independent molecules is similar to that observed for isoleucinomycin, cyclo[-(D-Ile-L-Lac-L-Ile-D-Hyi)3] [V. Z. Pletnev et al. (1980) Biopolymers, Vol. 19, pp. 1517-1534]. The structure has an asymmetric conformation stabilized by six intramolecular H bonds, five bonds being of the 4-->1 type and one bond being of the 5-->1 type. One water molecule is caged in the internal cavity of each cyclodepsipeptide. This conformation could represent an intermediate state between free and complexed forms of valinomycin.
缬氨霉素类似物环[（D-缬氨酸-L-乳酸-L-丙氨酸-D-羟基异亮氨酸）2（D-缬氨酸-L-乳酸-L-缬氨酸-D-羟基异亮氨酸）]的晶体和分子结构已通过“摇晃烘焙”程序的X射线直接法解析。从辛烷/二氯甲烷混合物中生长出的晶体属于空间群P2(1)（Z = 4），晶胞参数a = 10.29，b = 32.08，c = 18.73 Å，β = 97.05°，每个不对称单元包含两个分子。经过各向异性精修后，标准可靠性因子Rl = 0.058。两个独立分子的构象与异亮氨霉素环[（D-异亮氨酸-L-乳酸-L-异亮氨酸-D-羟基异亮氨酸）3] [V. Z. 普列特涅夫等人（1980年）《生物聚合物》，第19卷，第1517 - 1534页]所观察到的构象相似。该结构具有由六个分子内氢键稳定的不对称构象，其中五个键为4→1型，一个键为5→1型。每个环缩肽的内腔中包笼着一个水分子。这种构象可能代表缬氨霉素游离形式和复合形式之间的中间状态。
