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PubMed1990

Crystallization of the reovirus type 3 Dearing core. Crystal packing is determined by the lambda 2 protein.

Core particles of reovirus type 3 Dearing (T3D) crystallized in the face-centered cubic space group F432 with dimensions of 1270 A along each edge of the unit cell. Core particles of reovirus type 1 Lang (T1L) did not crystallize. Experiments with core particles derived from 27 different T1L x T3D reassortant viruses indicated that the L2 genome segment determined the capacity of cores to crystallize. This finding indicates important differences in the surface topography of the L2-translation product, the lambda 2 protein, of these two isolates, and suggests that important crystal contacts are mediated by this protein. These data are used to generate a model of the packing of reovirus core particles within the unit cell.

Crystallization↗

PubMed1989

Form-determining functions in Sindbis virus nucleocapsids: nucleosomelike organization of the nucleocapsid.

Purified intact Sindbis virus nucleocapsids were treated at different pH values or with various concentrations of divalent cations, cation chelators, salt, or formamide. The resulting structures were examined by velocity sedimentation, electron microscopy, and protein-protein cross-linking. Changes in each of the test conditions led to alterations in the sedimentation profile of treated nucleocapsids. Appropriate concentrations of formamide or divalent cations generated beaded strandlike structures similar in morphology to those generated from adenovirus cores and nucleosomes. The capsid protein and RNA remained associated with each other at NaCl concentrations less than or equal to 1 M or after treatment of the structures with alkaline pH up to and including pH 10.7. Protein and RNA were dissociated by salt concentrations of greater than 1 M, suggesting that the arginine-rich, amino-terminal portion of the capsid protein is responsible for binding the RNA. Protein-protein cross-linking also indicated that the capsid proteins remained associated in small aggregates under some of the conditions that caused dissociation of the nucleocapsid and suggested the presence of more than one type of protein-protein interaction in the nucleocapsids. Collectively, these data suggest that, like histones and adenovirus core proteins, the Sindbis virus capsid protein serves to package segments of the genome into nucleoprotein beads which are capable of interacting with each other to form the nucleocapsid structure.

Capsid↗