Journal Article

Backbone structure of the infectious ε15 virus capsid revealed by electron cryomicroscopy

Weigele, Peter R., Jiang, Wen, Jakana, Joanita, Baker, Matthew L., Chiu, Wah, King, Jonathan

2008

Overview

A half-century after the determination of the first three-dimensional crystal structure of a protein 1 , more than 40,000 structures ranging from single polypeptides to large assemblies have been reported 2 . The challenge for crystallographers, however, remains the growing of a diffracting crystal. Here we report the 4.5-Å resolution structure of a 22-MDa macromolecular assembly, the capsid of the infectious epsilon15 (ε15) particle, by single-particle electron cryomicroscopy. From this density map we constructed a complete backbone trace of its major capsid protein, gene product 7 (gp7). The structure reveals a similar protein architecture to that of other tailed double-stranded DNA viruses, even in the absence of detectable sequence similarity 3 , 4 . However, the connectivity of the secondary structure elements (topology) in gp7 is unique. Protruding densities are observed around the two-fold axes that cannot be accounted for by gp7. A subsequent proteomic analysis of the whole virus identifies these densities as gp10, a 12-kDa protein. Its structure, location and high binding affinity to the capsid indicate that the gp10 dimer functions as a molecular staple between neighbouring capsomeres to ensure the particle’s stability. Beyond ε15, this method potentially offers a new approach for modelling the backbone conformations of the protein subunits in other macromolecular assemblies at near-native solution states.

• Publisher: Nature Publishing Group UK,Nature Publishing
• Subject: Biological and medical sciences / Fundamental and applied biological sciences. Psychology / Humanities and Social Sciences / letter / Microbiology / Morphology, structure, chemical composition, physicochemical properties / multidisciplinary / Science / Science (multidisciplinary) / Virology