Abstract
During assembly and morphogenesis of Rous sarcoma virus (RSV), proteolytic processing of the structural precursor (Pr76Gag) protein generates three capsid (CA) protein variants, CA476, CA479, and CA488. The proteins share identical N-terminal domains (NTDs), but are truncated at residues corresponding to gag codons 476, 479, and 488 in their CA C-terminal domains (CTDs). To characterize oligomeric forms of the RSV CA variants, we examined 2D crystals of the capsid proteins, assembled on lipid monolayers. Using electron microscopy and image analysis approaches, the CA proteins were observed to organize in hexagonal (p6) arrangements, where rings of membrane-proximal NTD hexamers were spaced at 95 Å intervals. Differences between the oligomeric structures of the CA variants were most evident in membrane-distal regions, where apparent CTDs interconnect hexamer rings. In this region, CA488 connections were observed readily, while CA476 and CA479 contacts were resolved poorly, suggesting that in vivo processing of CA488 to the shorter forms may permit virions to adopt a dissembly-competent conformation. In addition to crystalline arrays, the CA479 and CA488 proteins formed small spherical particles with diameters of 165-175 Å. The spheres appear to be arranged from hexamer or hexamer plus pentamer ring subunits that are related to the 2D crystal forms. Our results implicate RSV CA hexamer rings as basic elements in the assembly of RSV virus cores.
Original language | English (US) |
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Pages (from-to) | 667-678 |
Number of pages | 12 |
Journal | Journal of Molecular Biology |
Volume | 316 |
Issue number | 3 |
DOIs | |
State | Published - 2002 |
Funding
We are grateful for assistance from laboratory members, including Ayna Alfadhli, Brian Arvidson, Liam Finlay, Zac Love, and Eric Steel. We appreciate helpful advice provided by Richard Henderson and Michael F. Schmid. This work was supported, in part, by NIGMS grants GM60170-03 (to E.B.), GM52914-07 (to E.B.), and CA52047 (to J.L.).
Keywords
- Capsid
- Electron microscopy
- Gag
- Retrovirus
- Rous sarcoma virus
ASJC Scopus subject areas
- Molecular Biology
- Structural Biology