Morag Omry, Sgourakis Nikolaos G, Baker David, Goldbourt Amir
School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Ramat Aviv 69978, Tel Aviv, Israel; and.
Department of Biochemistry, University of Washington, Seattle, WA 98195.
Proc Natl Acad Sci U S A. 2015 Jan 27;112(4):971-6. doi: 10.1073/pnas.1415393112. Epub 2015 Jan 13.
Filamentous phage are elongated semiflexible ssDNA viruses that infect bacteria. The M13 phage, belonging to the family inoviridae, has a length of ∼1 μm and a diameter of ∼7 nm. Here we present a structural model for the capsid of intact M13 bacteriophage using Rosetta model building guided by structure restraints obtained from magic-angle spinning solid-state NMR experimental data. The C5 subunit symmetry observed in fiber diffraction studies was enforced during model building. The structure consists of stacked pentamers with largely alpha helical subunits containing an N-terminal type II β-turn; there is a rise of 16.6-16.7 Å and a tilt of 36.1-36.6° between consecutive pentamers. The packing of the subunits is stabilized by a repeating hydrophobic stacking pocket; each subunit participates in four pockets by contributing different hydrophobic residues, which are spread along the subunit sequence. Our study provides, to our knowledge, the first magic-angle spinning NMR structure of an intact filamentous virus capsid and further demonstrates the strength of this technique as a method of choice to study noncrystalline, high-molecular-weight molecular assemblies.
丝状噬菌体是感染细菌的细长半柔性单链DNA病毒。属于丝状病毒科的M13噬菌体，长度约为1μm，直径约为7nm。在此，我们利用由魔角旋转固态核磁共振实验数据获得的结构限制条件，通过Rosetta建模，展示了完整M13噬菌体衣壳的结构模型。在模型构建过程中，强制保持了纤维衍射研究中观察到的C5亚基对称性。该结构由堆叠的五聚体组成，其亚基主要为α螺旋结构，含有一个N端II型β转角；连续五聚体之间的上升距离为16.6 - 16.7 Å，倾斜角度为36.1 - 36.6°。亚基的堆积通过一个重复的疏水堆积口袋得以稳定；每个亚基通过贡献不同的疏水残基参与四个口袋的形成，这些疏水残基沿亚基序列分布。据我们所知，我们的研究提供了首个完整丝状病毒衣壳的魔角旋转核磁共振结构，并进一步证明了该技术作为研究非晶态、高分子量分子聚集体的首选方法的优势。
