Siphoviridae and Myoviridae tail and head assemblies occur independently. Tail assembly follows a sequential order . The tail measure protein (or tape measure protein, ruler) determines the length of Sipho- and Myoviridae tails .
Tail tube protein polymerization starts from baseplate assembly . The tail measure protein possibly assembles with tail assembly chaperones, and the resulting complex interacts with baseplate to form the tail initiator. Tail tube protein polymerizes on this template and displaces the chaperones thereby creating the tube. It is unclear whether the tail measure protein is trapped inside.Once polymerization of the cylindrical part(s) of the tail has reached the expected length, terminator proteins stop the polymerization . In the phage lambda, the TMP is matured.
In many viruses, the tail assembly gene is expressed through a programmed translational frameshift and gives rise to two chaperone proteins with overlapping sequences .