Yang F, Forrer P, Dauter Z, Conway J F, Cheng N, Cerritelli M E, Steven A C, Plückthun A, Wlodawer A
Macromolecular Crystallography Laboratory, Program in Structural Biology, National Cancer Institute, Frederick Cancer Research and Development Center, Frederick, Maryland 21702, USA.
Nat Struct Biol. 2000 Mar;7(3):230-7. doi: 10.1038/73347.
The crystal structure of gpD, the capsid-stabilizing protein of bacteriophage lambda, was solved at 1.1 A resolution. Data were obtained from twinned crystals in space group P21 and refined with anisotropic temperature factors to an R-factor of 0.098 (Rfree = 0. 132). GpD (109 residues) has a novel fold with an unusually low content of regular secondary structure. Noncrystallographic trimers with substantial intersubunit interfaces were observed. The C-termini are well ordered and located on one side of the trimer, relatively far from its three-fold axis. The N-termini are disordered up to Ser 15, which is close to the three-fold axis and on the same side as the C-termini. A density map of the icosahedral viral capsid at 15 A resolution, obtained by cryo-electron microscopy and image reconstruction, reveals gpD trimers, seemingly indistinguishable from the ones seen in the crystals, at all three-fold sites. The map further reveals that the side of the trimer that binds to the capsid is the side on which both termini reside. Despite this orientation of the gpD trimer, fusion proteins connected by linker peptides to either terminus bind to the capsid, allowing protein and peptide display.
噬菌体λ的衣壳稳定蛋白gpD的晶体结构在1.1埃分辨率下得到解析。数据取自空间群P21的孪晶，并使用各向异性温度因子进行精修，最终R因子为0.098（Rfree = 0.132）。GpD（109个残基）具有一种新颖的折叠方式，其规则二级结构的含量异常低。观察到具有大量亚基间界面的非晶体三聚体。C末端排列有序，位于三聚体的一侧，相对远离其三重轴。N末端在Ser 15之前无序，Ser 15靠近三重轴且与C末端在同一侧。通过冷冻电子显微镜和图像重建获得的15埃分辨率的二十面体病毒衣壳密度图显示，在所有三重位点都有gpD三聚体，看起来与晶体中的三聚体没有区别。该图进一步显示，三聚体与衣壳结合的一侧是两个末端所在的一侧。尽管gpD三聚体有这样的取向，但通过连接肽连接到任一末端的融合蛋白都能与衣壳结合，从而实现蛋白质和肽的展示。
