Capsid protein that self-assembles to form an icosahedral capsid, about 54 nm in diameter. Part of the immature prohead complex. Interaction between the viral portal protein and the viral protease I may give rise to an early 25S initiator complex. The scaffolding protein Z and the capsid protein T should then be added to the initiator complex to yield immature procapsid (Probable). Host GroEL and GroES are also essential for the correct assembly of viral capsids. Capsid. Expressed in the late phase of the viral replicative cycle. Expression of late genes is activated by the viral late transcription activator C.