Structural elements in adenovirus cores

Abstract

"Freeze-fracture negative staining" of adenovirus type 5 revealed the virus cores as internal bodies with a fine granular surface which at high magnification shows reticular and ring-like patterns. This indicates that the virus protein V forms a thin surface layer for which a name "core shell" is proposed. Virus cores prepared by heating virus particles in sodium deoxycholate (DOC) relaxed into curved filaments or several rods by means of EGTA and high salt, respectively. High pH treatment had similar effects as high salt. Rod-like elements were also observed in ultrathin sections of the "DOC-cores". Fresh cores exhibited circular dichroism (C.D.) with similar features as described for nucleosomes (COWMAN and FASMAN, ref. 5). This indicates that the DNA has an orderly arrangement in the cores. EGTA had no effect on C.D. spectra but high salt treatment abolished the positive peak in 10 minutes. It is concluded that the adenovirus nucleocapsid is a linear structure, presumably a 120-150 Angstrom thick filament folded 5 to 6 times into "rods" as previously observed by freeze-fracturing.

The structure of nucleoprotein cores released from adenovirions

“…This value (which must be an overestimate for the core fibre does not entirely occupy the space of a solid cylinder of these dimensions ( Figure 2)) is in reasonable agreement with the volume of the spherical space available within the capsid shell (V= 4/3 wrr3 where r, the internal diameter of the virion, is taken as 75nm (23 and our measurements)), 2.2x105 nm3, into which the core must be packed. This description is also consistent with the presence of 'rod-like' elements reported by Nermut (38) and the 21nm (210A) particles described by Brown and colleagues (23): in the more compact forms described by these authors adjacent segments of the folded double fibre would appear as units of about 20nm. Indeed, the image shown in panel e of Figure 1 is very reminiscent of those reported by Brown and colleagues ( Figure 8 of reference 23).…”

“…Panel f illustrates the typical structure seen when purified virions were exposed to 0.5% (w/v) sodium deoxycholate for 3 minutes at 580C. granular surface (Figure 1, panels a and b) are very similar to those seen in previous experiments (5,12,23,37,38), as are compact structures from which strings or loops radiate (Figure 1 panel b; 23,37,38). The diameter of shadowed core particles, 125±25 nm based on 99 examples, is somewhat larger than the diameter of the virion of 87nm measured by Brown and colleagues (23).…”

Internal structural anisotropy of spherical viruses studied with magnetic birefringence.

“…The core contains double-stranded DNA in association with four species of protein. The nucleoprotein may be in the form of folded rods (Nermut, 1979) with a structure akin to chromatin (Corden et al, 1976;Mirza and Weber, 1982). The outer envelope of influenza virus, recently shown to be spherical in solution (Mellema et al, 1981), is a lipid bilayer from which project two types of glycoprotein.…”