Lander Gabriel C, Evilevitch Alex, Jeembaeva Meerim, Potter Clinton S, Carragher Bridget, Johnson John E
National Resource for Automated Molecular Microscopy, The Scripps Research Institute, La Jolla, CA 92037, USA.
Structure. 2008 Sep 10;16(9):1399-406. doi: 10.1016/j.str.2008.05.016.
We report the cryo-EM structure of bacteriophage lambda and the mechanism for stabilizing the 20-A-thick capsid containing the dsDNA genome. The crystal structure of the HK97 bacteriophage capsid fits most of the T = 7 lambda particle density with only minor adjustment. A prominent surface feature at the 3-fold axes corresponds to the cementing protein gpD, which is necessary for stabilization of the capsid shell. Its position coincides with the location of the covalent cross-link formed in the docked HK97 crystal structure, suggesting an evolutionary replacement of this gene product in lambda by autocatalytic chemistry in HK97. The crystal structure of the trimeric gpD, in which the 14 N-terminal residues required for capsid binding are disordered, fits precisely into the corresponding EM density. The N-terminal residues of gpD are well ordered in the cryo-EM density, adding a strand to a beta-sheet formed by the capsid proteins and explaining the mechanism of particle stabilization.
我们报道了噬菌体λ的冷冻电镜结构以及稳定包含双链DNA基因组的20埃厚衣壳的机制。HK97噬菌体衣壳的晶体结构只需进行微小调整就能与大部分T = 7 λ颗粒密度相匹配。在三重轴处一个突出的表面特征对应于胶结蛋白gpD，它对于衣壳壳的稳定是必需的。其位置与对接的HK97晶体结构中形成的共价交联位置一致，这表明λ中该基因产物在进化过程中被HK97中的自催化化学所取代。三聚体gpD的晶体结构中，衣壳结合所需的14个N端残基无序，却能精确地契合相应的电镜密度。gpD的N端残基在冷冻电镜密度中排列有序，为衣壳蛋白形成的β折叠增加了一条链，解释了颗粒稳定的机制。
