Near-Atomic Resolution Structure of a Plant Geminivirus Determined by Electron Cryomicroscopy

• DOI: 10.1016/j.str.2017.06.013
• Publication Date: 2017-07-14T14:35:02Z
• Authors: Katharina Hipp; Clemens Grimm; Holger Jeske; Bettina Böttcher
• Keywords: 0301 basic medicine; 03 medical and health sciences; Binding Sites; Geminiviridae; Begomovirus; Cryoelectron Microscopy; Capsid Proteins; DNA; Protein Binding

African cassava mosaic virus is a whitefly-transmitted geminivirus which forms unique twin particles of incomplete icosahedra that are joined at five-fold vertices, building an unusual waist. How its 22 capsomers interact within a half-capsid or across the waist is unknown thus far. Using electron cryo-microscopy and image processing, we determined the virion structure with a resolution of 4.2 Å and built an atomic model for its capsid protein. The inter-capsomer contacts mediated by the flexible N termini and loop regions differed within the half-capsids and at the waist, explaining partly the unusual twin structure. The tip of the pentameric capsomer is sealed by a plug formed by a turn region harboring the evolutionary conserved residue Y193. Basic amino acid residues inside the capsid form a positively charged pocket next to the five-fold axis of the capsomer suitable for binding DNA. Within this pocket, density most likely corresponding to DNA was resolved.