Capsomere

The capsomere is a subunit of the capsid, an outer covering of protein that protects the genetic material of a virus.

Two types of capsomeres constitute the icosahedral capsid: pentagonal (pentons) at the vertices and hexagonal (hexons) at the faces.

In electron micrographs, capsomeres are recognized as regularly spaced rings with a central hole.

The capsomeres protect against physical, chemical, and enzymatic damage and are multiply redundant; having a few protein subunits that are repeated.

This is because the viral genome is being as economic as possible by only needing a few protein codons to make a large structure.

In this diagram of an Adenovirus , the capsid molecules are clearly visible.