Electron Microscopy of Tubular Assemblies Associated with Naturally Occurring Bovine Rotavirus

Biochemical Evidence for the Oligomeric Arrangement of Bovine Rotavirus Nucleocapsid Protein and Its Possible Significance in the Immunogenicity of This Protein

“…The demonstration ofa rotavirus nucleocapsid protein trimeric complex in virus particles and in infected cells supports previous reports suggesting this type of nucleocapsid arrangement (Chasey & Labram, 1983;Gorziglia et al, 1985;Martin et at., 1975;Novo & Esparza, 198I ;Palmer et al, 1977;Petrie et al, 1982). Novo & Esparza (1981) first suggested that this was the case, on the basis of velocity sedimentation and gel filtration studies of infected cell extracts.…”

“…Since the nucleocapsid protein constitutes approximately 80 ~ of the protein in single-shelled particles, the arrangement of this protein has been the focus of many studies (Chasey & Labram, 1983;Martin et al, 1975;Palmer et al, 1977;Palmer & Martin, 1982;Petrie et al, 1982;Sabara et aL, 1985). Electron microscopical examination of virus particles suggested the arrangement of inner capsid subunits into an open mesh exhibiting a regular pattern of holes (Martin et al, 1975).…”

Biochemical Evidence for the Oligomeric (Possibly Trimeric) Structure of the Major Inner Capsid Polypeptide (45K) of Rotaviruses

“…We have also found that the reassembly of subunits liberated after disruption of rotavirus particles by ammonium molybdate treatment leads to the formation of tubular structures and disorganized sheets (Esparza & Gil, 1978). Some of the tubules observed in human and bovine rotavirus preparations exhibit a hexagonal surface lattice similar to that described for human rotaviruses (Chasey & Labram, 1983).…”

“…Morphological subunits of the rotavirus inner capsid do show a triangular shape (Martin et al, 1975), which on closer examination demonstrates a central hole surrounded by three smaller subunits (Esparza & Gil, 1978). The 'rotatube 1' structures described by Chasey & Labram (1983), when examined by optical diffraction methods, appeared to be composed of hexagonal units, each consisting of a ring of six subunits, in which 'light' and 'dark' subunits alternate, suggesting some dissimilarity in their shape or position. Chasey & Labram (1983) concluded that if each subunit is indeed trimeric, it could offer an explanation for their apparent difference in orientation: each identical trimer, having three directions in which to link with equivalent sites in adjacent units, rotates by 180 ° with respect to its neighbours.…”

“…The 'rotatube 1' structures described by Chasey & Labram (1983), when examined by optical diffraction methods, appeared to be composed of hexagonal units, each consisting of a ring of six subunits, in which 'light' and 'dark' subunits alternate, suggesting some dissimilarity in their shape or position. Chasey & Labram (1983) concluded that if each subunit is indeed trimeric, it could offer an explanation for their apparent difference in orientation: each identical trimer, having three directions in which to link with equivalent sites in adjacent units, rotates by 180 ° with respect to its neighbours. Furthermore biochemical evidence has indicated that the morphological subunits of the rotavirus inner capsid are formed by the p45K polypeptide (Novo & Esparza, 1981 ;Bican et al, 1982), making it easier to favour the trimeric nature of the p45K oligomer reported in the present paper.…”