Forms the small spikes on the baseplate that plug the end of the tube before DNA ejection and form a channel perforating the host membrane during ejection. Involved in baseplate assembly. Binds 1 calcium ion per spike trimer. Binds 1 Fe cation per spike trimer. Binds 1 chloride per spike trimer. homotrimer. Part of the virion tail. Expressed in the late phase of the viral replicative cycle. Belongs to the P2likevirus spike protein family.