期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：4
页码：971-976
DOI：10.1073/pnas.1415393112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceWe present an atomic-resolution structure of the M13 filamentous bacteriophage capsid, one of many filamentous viruses that play important roles in many areas of research. The model was obtained by combining magic-angle spinning NMR and Rosetta modeling, used for the first time, to our knowledge, to derive the atomic structure of an intact virus capsid. The structure is made up of thousands of identical helical subunits stabilized by repeating hydrophobic pockets, which serve as a locking motif, suggesting a direct role in phage particle assembly. Analysis of various phage sequences suggests the presence of a conserved design principle for helical capsids. Because the current method does not rely on any particular preparation procedure, it can be applied to other viral capsids and molecular assemblies. Filamentous phage are elongated semiflexible ssDNA viruses that infect bacteria. The M13 phage, belonging to the family inoviridae, has a length of [~]1 m 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 {beta}-turn; there is a rise of 16.6-16.7 [IMG]f1.gif" ALT="A" BORDER="0"> and a tilt of 36.1-36.6{degrees} 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.
