The reovirus cell attachment protein possesses two independently active trimerization domains: basis of dominant negative effects.
The reovirus cell attachment protein, sigma 1, is a homotrimer with an N-terminal fibrous tail and a C-terminal globular head. By cotranslating full-length and various truncated sigma 1 proteins in vitro, we show that the N- and C-terminal halves of sigma 1 possess independent trimerization and folding domains. Trimerization of sigma 1 is initiated at the N-terminus by the formation of a "loose," protease-sensitive, three-stranded, alpha-helical coiled coil. This serves to bring the three unfolded C-termini into close proximity to one another, facilitating their subsequent trimerization and cooperative folding. Concomitant with, but independent of, this latter process, the N-terminal fiber further matures into a more stable and protease-resistant structure. The coordinated folding of sigma 1 trimers exemplifies the dominant negative effects of mutant subunits in oligomeric complexes.
Leone
G
G
Department of Microbiology and Infectious Diseases, University of Calgary Health Sciences Center, Alberta, Canada.
Maybaum
L
L
Lee
P W
PW
D036022:Capsid Proteins; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012087:Reoviridae / Q000737:chemistry*; D014764:Viral Proteins / Q000737:chemistry*
D036022:Capsid Proteins; D014764:Viral Proteins; C031728:sigma 1 protein, reovirus