A prohead or procapsid is an immature viral

capsid A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may ...

structure formed in the early stages of self-assembly of some bacteriophages, including the ''

Caudovirales ''Caudovirales'' is an order of viruses known as the tailed bacteriophages (''cauda'' is Latin for "tail"). Under the Baltimore classification scheme, the ''Caudovirales'' are group I viruses as they have double stranded DNA (dsDNA) genomes, ...

'' or tailed bacteriophages. Production and assembly of stable proheads is an essential precursor to bacteriophage genome packaging; this packaging activity can be replicated ''in vitro''. The prohead structure may take a different shape from the head of a mature virion, as seen with the prohead of Bacillus subtilis phage φ29.

References

Bacteriophages {{virus-stub