Structural elements in adenovirus cores. Evidence for a "core shell" and linear structures in "relaxed" 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.