RNA mediated protein switching in the assembly of a quasi equivalent animal virus

John E. Johnson, Fan Dong, Vijay Reddy, A. S. Macromolecule

Research output: Contribution to journalArticlepeer-review


A defining feature of biological chemistry is the appearance of multiple molecular conformations that are dependent on the particular interactions experienced by the macromolecule.The initial understanding of this phenomena was developed from studies of quasi-equivalent icosahedral virus particles where identical gene products were found in slightly different environments. The principles of quasi-equivalence are now seen to be ubiquitous in biology and molecular switching is found in processes as diverse as signal transaction and nucleosome assembly. Virus particles continue to be exceptionally good examples for understanding this phenomena because there is an adequate number of nigh resolution structures to provide an inventory of molecular switches that demonstrate the diversity of chemical mechanisms for achieving quasi equivalence. We investigated molecular switching in T=3 and T=4 quasi equivalent animal viruses using crystallography, molecular genetics and computational chemistry. The T=3 Flock House Virus (FHV) utilizes both a 10 amino acid flexible protein segment and a 12 base pair duplex RNA to dramatically alter the dihedral angles between protein junctions in the capsid. We have made mutants of FHV in which the peptide observed in switching was genetically removed and the resultant polypeptide was expressed in a baculovirus system. The resulting assembly products are a distribution of discrete particles that include a native-like T-3 particle (crystallized and solved at 2.6A resolution) and three other particles that were modeled by assuming interactions of the type observed in a native T=3 particle, but not distributed with icosahedral symmetry. The switching observed m the T=4 Nudaurelia u> capensis virus (No>V) is conceptually similar to the switching observed in the T=J virus, but here the contacts are mediated by only a flexible polypeptide. By examining the different polymorphic forms of FHV and by comparing these with the NωV "protein only switching we are developing principles to define the chemistry and energetics required for quasiequivalent interactions.

Original languageEnglish (US)
Pages (from-to)A1332
JournalFASEB Journal
Issue number8
StatePublished - 1998
Externally publishedYes


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