The baseplate of bacteriophage T4 controls host cell recognition, attachment, tail sheath contraction and viral DNA ejection. The structure of the baseplate suggests a mechanism of baseplate structural transition during the initial stages of T4 infection. The baseplate is assembled from six identical wedges that surround the central hub. Gp53, along with other T4 gene products, combine sequentially to assemble a wedge [1].

1: Three-dimensional structure of bacteriophage T4 baseplate. Kostyuchenko VA, Leiman PG, Chipman PR, Kanamaru S, van Raaij MJ, Arisaka F, Mesyanzhinov VV, Rossmann MG; Nat Struct Biol. 2003;10:688-693. PMID:12923574