Langs D A, Blessing R H, Duax W L
Medical Foundation of Buffalo, Inc., NY.
Int J Pept Protein Res. 1992 Apr;39(4):291-9. doi: 10.1111/j.1399-3011.1992.tb01588.x.
Valinomycin, cyclo-[(L-Val-D-Hyv-D-Val-L-Lac)3-], was crystallized from aqueous dioxane solvent as a monohydrate complex in which water molecules were found within the ion-binding cavity of the ionophore: monoclinic P2(1), a = 14.377 (3), b = 41.554 (14), c = 14.080 (3) A, beta = 118.27 (2) degrees, Z = 4. There are two non-equivalent valinomycin-water complexes and three dioxane molecules in the asymmetric unit. The ionophore molecules adopt two similar but non-identical, octahedral, bracelet, cage conformations that are a consequence of two distinct ways in which the complexed water molecules can deform the normal octahedral coordinate geometry of the metal binding site. In the first complex the water molecule forms hydrogen donor bonds to the carbonyl oxygens of two L-valine residues on one facial side of the cavity, while in the second complex the water molecule is trigonal-planar coordinate and binds to two L-valine residues on one entrant face of the cavity plus a third D-valine residue from the opposite side of the cavity.
缬氨霉素，环[（L-缬氨酸-D-羟基缬氨酸-D-缬氨酸-L-乳酸）3-]，从含水二氧六环溶剂中结晶为一水合物络合物，其中在离子载体的离子结合腔内发现了水分子：单斜晶系P2(1)，a = 14.377 (3)，b = 41.554 (14)，c = 14.080 (3) Å，β = 118.27 (2)°，Z = 4。不对称单元中有两个不等价的缬氨霉素-水络合物和三个二氧六环分子。离子载体分子采取两种相似但不相同的八面体、手镯状、笼状构象，这是由于络合水分子使金属结合位点的正常八面体配位几何发生变形的两种不同方式导致的。在第一个络合物中，水分子与腔内一侧一个面的两个L-缬氨酸残基的羰基氧形成氢键供体键，而在第二个络合物中，水分子呈三角平面配位，与腔内一个入口面的两个L-缬氨酸残基以及来自腔对面的第三个D-缬氨酸残基结合。
