10779/crick.12588962.v1 Neil J Ball Neil J Ball Giuseppe Nicastro Giuseppe Nicastro Moumita Dutta Moumita Dutta Dominic J Pollard Dominic J Pollard David C Goldstone David C Goldstone Marta Sanz-Ramos Marta Sanz-Ramos Andres Ramos Andres Ramos Erik Müllers Erik Müllers Kristin Stirnnagel Kristin Stirnnagel Nicole Stanke Nicole Stanke Dirk Lindemann Dirk Lindemann Jonathan P Stoye Jonathan P Stoye William R Taylor William R Taylor Peter B Rosenthal Peter B Rosenthal Ian A Taylor Ian A Taylor Structure of a spumaretrovirus gag central domain reveals an ancient retroviral capsid The Francis Crick Institute 2020 Amino Acid Sequence Animals Blotting, Western Capsid Capsid Proteins Cell Line Gene Products, gag Humans Nuclear Magnetic Resonance, Biomolecular Protein Conformation Real-Time Polymerase Chain Reaction Spumavirus Virus Assembly Taylor, I FC001178 Stoye FC001162 Rosenthal FC001143 Taylor, W FC001179 Virology 0605 Microbiology 1107 Immunology 1108 Medical Microbiology 2020-07-01 11:41:35 Journal contribution https://crick.figshare.com/articles/journal_contribution/Structure_of_a_spumaretrovirus_gag_central_domain_reveals_an_ancient_retroviral_capsid/12588962 The Spumaretrovirinae, or foamy viruses (FVs) are complex retroviruses that infect many species of monkey and ape. Despite little sequence homology, FV and orthoretroviral Gag proteins perform equivalent functions, including genome packaging, virion assembly, trafficking and membrane targeting. However, there is a paucity of structural information for FVs and it is unclear how disparate FV and orthoretroviral Gag molecules share the same function. To probe the functional overlap of FV and orthoretroviral Gag we have determined the structure of a central region of Gag from the Prototype FV (PFV). The structure comprises two all α-helical domains NtDCEN and CtDCEN that although they have no sequence similarity, we show they share the same core fold as the N- (NtDCA) and C-terminal domains (CtDCA) of archetypal orthoretroviral capsid protein (CA). Moreover, structural comparisons with orthoretroviral CA align PFV NtDCEN and CtDCEN with NtDCA and CtDCA respectively. Further in vitro and functional virological assays reveal that residues making inter-domain NtDCEN-CtDCEN interactions are required for PFV capsid assembly and that intact capsid is required for PFV reverse transcription. These data provide the first information that relates the Gag proteins of Spuma and Orthoretrovirinae and suggests a common ancestor for both lineages containing an ancient CA fold.