Premium
Frozen‐fractured viruses; a study of virus structure using freeze‐etching
Author(s) -
Willison J. H. M.,
Cocking E. C.
Publication year - 1972
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1111/j.1365-2818.1972.tb01041.x
Subject(s) - capsid , tobacco mosaic virus , virus , icosahedral symmetry , mosaic virus , virology , biology , chemistry , materials science , biophysics , crystallography , plant virus
SUMMARY Tobacco mosaic virus (TMV), tobacco rattle virus (TRV), Tipula iridescent virus (TIV), turnip yellow mosaic virus (TYMV), T 2 phage and Lambda phage were examined by freeze‐etching water/glycerol suspensions. It was found that the virus particles usually fracture internally. TMV rarely fractures at its surface. Careful consideration of the fracture planes within TMV indicates not only that the TMV subunits do not fracture but also that there are no ‘preferred planes’ of fracture. An unexpected channel appears at the position of the RNA in TMV on one side of the capsid only. It is proposed that this indicates that the fracture of RNA is out of step with that of the subunit. By deep‐etching, a 5 nm repeat can sometimes be seen at the capsid surface of TMV (vulgare). TRV sometimes fractures to reveal its surface. It is proposed that this indicates that the surface of this rod‐shaped virus is smoother than that of the similar TMV. The large icosahedral virus, TIV, fractures between core and coat protein. The core which appears to consist of globular subunits is icosahedral and fits closely into its enclosing coat. The coat thickness is 10–12 nm. Numerous collapsible fibrous projections (probably up to 150 nm long) project from the surface of the coat. T 2 phage sometimes fractures to reveal the surface of the enclosed DNA which is smooth and very compact. Fracture by the freeze‐etch technique is shown to be a valuable adjunct to other techniques for the study of virus structure. It can reveal otherwise hidden internal structures. It may also disclose planes of minimum chemical bond energies represented by recurring regular fracture planes. The technique appears to be unsuitable, however, for the smaller viruses TYMV and Lambda phage.