Component of the baseplate that forms a central needlelike spike used to puncture the host cell membrane for tube insertion during virus entry. Probably involved in baseplate and tail assembly. Serves as the distal plug of tail tube channel and might regulate the process of the phage DNA and protein ejection into the host cell. Binds 1 Ca(2+) cation per trimer. Ca(2+) plays an important role in interaction with the host cell membrane. Binds 1 Cl(-) ion per trimer. Binds 1 Fe cation per trimer. Homotrimer (PubMed:20478417, PubMed:22922659). Part of a complex composed of three DNA circularization protein N, three baseplate hub protein gp44 and three sub-complex wedge (made of two copies of each baseplate protein gp46, gp47 and gp48) that forms the baseplate (PubMed:27555589). Baseplate protein. Expressed in the late phase of the viral replicative cycle. Expression of late genes is activated by the viral late transcription activator C. The C-terminus is a needlelike shaped homotrimer consisting of an intertwined beta-sheet, a triple beta-helix and a metal-binding region. No tail is synthesized. Translation initiates from a non-canonical start codon (GUG).