Bovine leukemia virus (BLV) is a deltaretrovirus that is found in domestic cattle. The structural protein Gag, found in all retroviruses, is comprised of three functional domains: matrix (MA), capsid (CA), and nucleocapsid (NC). Previous studies have shown that both BLV MA and NC are able to bind to nucleic acids as individual proteins. Compared to lentiviruses, little is known about the structure of the Gag polyprotein of deltaretroviruses; although Gag is proteolyzed during maturation, a wealth of information exists that has shown the full-length Gag to be critical for assembly of immature virus particles and packaging of viral genomic RNA. In this work, a structural model for BLV Gag is presented as a combination of previous structural data, homology modeling, and flexible fitting to SAXS data. The model was used in molecular dynamics simulations to determine the relative mobility of the protein backbone. Functional annealing assays were performed to elucidate the mechanism of interaction between BLV Gag and nucleic acids. Our results show that full-length BLV Gag has a fairly rigid structure that is rod-shaped, with the exception of the linker between the MA and CA domains. Additionally, Gag-facilitated annealing is faster but less complete in the absence of the MA domain, indicating that the MA and NC domains are both involved during the process of RNA packaging.

Molecular structure of bovine leukemia virus gag polyprotein determined by SAXS and computational modeling

2019 Spring National Meeting

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