The packaging of DNA into the procapsid requires a molecular motor, which uses ATP as energy to accomplish the energetically unfavorable motion.

In some bacteriophage, an RNA (pRNA) molecule is a vital component of this motor.

[1] Structural analyses of the packaging motor have demonstrated that the pRNA molecule has fivefold symmetry when attached to the prohead.

[2][3][4] The pRNA is thought to be bound by the capsid connector protein.

[6] Nuclear cleavage occurs in the single strand region linking these two domains.