AI Article Synopsis
- The orthoretroviral capsid protein (CA) is crucial for forming the shell around the viral genome, undergoing a maturation process where a hydrophobic spacer peptide (SP) is gradually removed.
- In vitro, RSV CA can assemble into hexamer tubes at near-physiological temperatures, influenced by electrostatic effects, forming multi-layered structures unless the spacer peptide is present in low amounts, which results in single-layered tubes.
- This assembly process helps visualize the tube structure through advanced techniques like cryo-electron microscopy, providing insights into the capsid's basic architecture and preventing the formation of irregular multi-layered structures.
Article Abstract
During a proteolytically-driven maturation process, the orthoretroviral capsid protein (CA) assembles to form the convex shell that surrounds the viral genome. In some orthoretroviruses, including Rous Sarcoma Virus (RSV), CA carries a short and hydrophobic spacer peptide (SP) at its C-terminus early in the maturation process, which is progressively removed as maturation proceeds. In this work, we show that RSV CA assembles in vitro at near-physiological temperatures, forming hexamer tubes that effectively model the mature capsid surface. Tube assembly is strongly influenced by electrostatic effects, and is a nucleated process that remains thermodynamically favored at lower temperatures, but is effectively arrested by the large Gibbs energy barrier associated with nucleation. RSV CA tubes are multi-layered, being formed by nested and concentric tubes of capsid hexamers. However the spacer peptide acts as a layering determinant during tube assembly. If only a minor fraction of CA-SP is present, multi-layered tube formation is blocked, and single-layered tubes predominate. This likely prevents formation of biologically aberrant multi-layered capsids in the virion. The generation of single-layered hexamer tubes facilitated 3D helical image reconstruction from cryo-electron microscopy data, revealing the basic tube architecture.
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| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5460288 | PMC |
| http://dx.doi.org/10.1038/s41598-017-02060-0 | DOI Listing |
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