Plays a role in tail tip complex assembly. The tail tip complex is assembled successively with three tail tip proteins J, one tail tip protein I, one tail tip protein L and one tail tip protein K. The tail tip complex interacts with tail measure protein to initiate tail tube assembly. The formation of the tail tip complex is completed by the addition of tail tip protein M, which is followed by tail tube polymerization. May be excluded form tail tip during maturation and would be absent from virions. May be involved in tail measure protein processing. Belongs to the peptidase C40 family.