Capsomer

The viral genome is not present unprotected, but is always packed in a protein coat. The protein envelope of the genome is the capsid . Capsids are composed of symmetrical building blocks, the caspsomers.

Capsomers can consist of a single polypeptide chain or they can be composed of several, different polypeptide chains (e.g. poliovirus). The complex of capsid and nucleic acid is called the nucleocapsid of a virus.

Depending on the number and composition of the proteins used and the type of nucleic acid of the virus, the nuekleocapsids result in 2 forms:

1. helical symmetry in the form of a spirally arranged nucleic acid, which is packaged in only one protein

2. cubic symmetry in the form of an icosahedron which, by using a capsomer consisting of several polypeptide chains, results in a polygon with different symmetry axes.

1. Hof H (2019). General virology. In: Hof H, Schlüter D, Dörries R, eds Duale Reihe Medizinische Mikrobiologie. 7th, completely revised and expanded edition. Stuttgart: Thieme S 170