Karle I L, Flippen-Anderson J L, Agarwalla S, Balaram P
Laboratory for the Structure of Matter, Naval Research Laboratory, Washington, DC 20375-5000.
Proc Natl Acad Sci U S A. 1991 Jun 15;88(12):5307-11. doi: 10.1073/pnas.88.12.5307.
Structures in four different crystal forms of [Leu1]zervamicin (zervamicin Z-L, Ac-Leu-Ile-Gln-Iva-Ile5-Thr-Aib-Leu-Aib-Hyp10-Gln-Aib-Hyp-Aib-P ro15-Phol, where Iva is isovaline, Aib is alpha-amino isobutyric acid, Hyp is 4-hydroxyproline, and Phol is phenylalaninol), a membrane channel-forming polypeptide from Emericellopsis salmosynnemata, have been determined by x-ray diffraction. The helical structure is amphiphilic with all the polar moieties on the convex side of the bent helix. Helices are bent at Hyp10 from approximately 30 degrees to approximately 45 degrees in the different crystal forms. In all crystal forms, the peptide helices aggregate in a similar fashion to form water channels that are interrupted by hydrogen bonds between N epsilon H(Gln11) and O delta (Hyp10) of adjacent helices. The Gln11 side chain is folded in an unusual fashion in order to close the channel. Space is available for an extended conformation for Gln11, in which case the channel would be open, suggesting a gating mechanism for cation transport. Structural details are presented for one crystal form derived from methanol/water solution: C85H140N18O22. 10H2O, space group P21, a = 23.068(6) A, b = 9.162(3) A, c = 26.727(9) A, beta = 108.69(2) degrees (standard deviation of last digit is given in parentheses); overall agreement factor R = 10.1% for 5322 observed relfections [magnitude of Fo greater than 3 sigma (F)]; resolution, 0.93 A.
[亮氨酸1]泽尔瓦霉素（泽尔瓦霉素Z-L，Ac-Leu-Ile-Gln-Iva-Ile5-Thr-Aib-Leu-Aib-Hyp10-Gln-Aib-Hyp-Aib-Pro15-Phol，其中Iva是异缬氨酸，Aib是α-氨基异丁酸，Hyp是4-羟基脯氨酸，Phol是苯丙氨醇）是来自鲑鱼艾美耳球囊霉的一种形成膜通道的多肽，其四种不同晶体形式的结构已通过X射线衍射确定。螺旋结构是两亲性的，所有极性部分都在弯曲螺旋的凸面。在不同晶体形式中，螺旋在Hyp10处从大约30度弯曲到大约45度。在所有晶体形式中，肽螺旋以相似的方式聚集形成水通道，这些水通道被相邻螺旋的NεH（Gln11）和Oδ（Hyp10）之间的氢键中断。Gln11侧链以不寻常的方式折叠以关闭通道。Gln11有空间形成伸展构象，在这种情况下通道将是开放的，这表明存在阳离子运输的门控机制。给出了一种源自甲醇/水溶液的晶体形式的结构细节：C85H140N18O22·10H2O，空间群P21，a = 23.068(6) Å，b = 9.162(3) Å，c = 26.727(9) Å，β = 108.69(2)度（括号中给出最后一位数字的标准偏差）；对于5322个观测反射[|Fo|大于3σ(F)]，总体一致性因子R = 10.1%；分辨率为0.93 Å。
