Sigma 1 protein of mammalian reoviruses extends from the surfaces of viral particles

Abstract

Electron microscopy revealed structures consisting of long fibers topped with knobs extending from the surfaces of virions of mammalian reoviruses. The morphology of these structures was reminiscent of the fiber protein of adenovirus. Fibers were also seen extending from the reovirus top component and intermediate subviral particles but not from cores, suggesting that the fibers consist of either the ,ulC or ol outer capsid protein. Amino acid sequence analysis predicts that the reovirus cell attachment protein al contains an extended fiber domain (R. Bassel-Duby, A.

The N-terminal heptad repeat region of reovirus cell attachment protein σ1 is responsible for σ1 oligomer stability and possesses intrinsic oligomerization function

“…where a and d are characteristically apolar residues, further indicates the propensity of this region to adopt a coiled-coil rope-like structure. Such theoretical considerations are clearly compatible with the fibrous morphology of al as revealed by electron microscopy (Furlong et al, 1988;Banerjea et al, 1988;Fraser et a/., 1990) and with the present demonstration that the heptad repeat region alone, when synthesized in an in vitro system, is capable of forming dimeric and trimeric structures whose stability is remarkably similar to that of the trimeric Nterminal tryptic fragment or of the native al oligomer. In view of the recent speculations on the structural and functional aspects of the "leucine zipper," we consider our direct demonstration that the heptad repeat possesses intrinsic dimerization and trimerization function to be significant (see also note added in proof).…”

“…The reovirus cell attachment protein (protein ~1) is strategically located at the twelve vertices of the outer capsid of the viral icosahedron (Lee et al, 1981;Furlong eta/., 1988) and plays a pivotal role in viral infectivity and tissue tropism (Sharpe and Fields, 1985). In electron microscopy, this protein can sometimes be seen as lollipop-shaped structures with proximal fibrous tails and distal globular heads projecting from the surfaces of viral particles (Furlong et a/., 1988). Protein al purified from reovirions or from a vaccinia expression system also has a similar morphology (Furlong et a/., 1988;Banerjea et a/., 1988;Fraser et a/., 1990).…”

“…In electron microscopy, this protein can sometimes be seen as lollipop-shaped structures with proximal fibrous tails and distal globular heads projecting from the surfaces of viral particles (Furlong et a/., 1988). Protein al purified from reovirions or from a vaccinia expression system also has a similar morphology (Furlong et a/., 1988;Banerjea et a/., 1988;Fraser et a/., 1990). The observations that the C-terminal half of al contains the receptor-binding domain (Nagata et al, 1987;Yeung et a/., 1989) and the N-terminal onequarter possesses intrinsic virion-anchoring property (Mah et a/., 1990) suggest that the fibrous tail and the globular head represent the N-and C-terminal portions, respectively, of this protein.…”

Virological and molecular characterization of a mammalian orthoreovirus type 3 strain isolated from a dog in Italy

“…Neutralization and HA activities are restricted to a single reovirus gene segment, S1 (Weiner and Fields, 1977), that encodes for s1 and s1s proteins. The s1 protein, a fibrous trimer located on the outer capsid of the virion (Fraser et al, 1990;Furlong et al, 1988), is responsible for viral attachment on cellular receptors (Lee et al, 1981;Weiner et al, 1980), serotype-specific neutralization (Bassel-Duby et al, 1986) and hemagglutination (Weiner et al, 1978). Analysis of the S1 gene of MRVs belonging to different serotypes has shown a strict correlation between sequence similarity and viral serotype (Cashdollar et al, 1985;Duncan et al, 1990;Nibert et al, 1990).…”

Biochemical and biophysical characterization of the reovirus cell attachment protein σ1: Evidence that it is a homotrimer

“…Of all the proteins encoded by the double-stranded RNA genomic segments of reovirus, the e1 protein has been most thoroughly studied . Protein al is a minor outer capsid protein situated at each vertex of the outer capsid of the viral icosahedron (Lee et al, 1981 ;Furlong et at, 1988) . This protein functions as the reovirus cell attachment protein (Lee et at, 1981 ;Armstrong et al, 1984) and the viral hemagglutinin (Weiner et al, 1978 ;Yeung et al ., 1987) .…”