Bacteriophage Ecology Group

Bacteriophage Ecology Group Bacteriophage Ecology Group

Capsid

The protein shell that encloses the nucleic acid genome of phages along with genomes of viruses in general (sometimes called a capsule instead).

In tailed phages the capsid is combined with a tail, which is responsible for adsorption as well as translocation of the phage DNA into the adsorbed bacterium.

The more complex a virion, the more types of proteins that make up its capsid. Regardless of the number of types of capsid proteins, a.k.a., capsomers, the capsid itself consists of multiply repeating multi-protein motifs. The capsids of most phages takes on an icosahedron shape which is either symmetrical or elongated. The prominent exception are the filamentous phages which possess helically shaped capsids rather than icosahedral. From the glossary of The Bacteriophage Lambda (1971) (p. 773): "The proteinaceous 'shell' or 'coat' of a phage particle, normally filled with nucleic acid to form the 'head.'"

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