1.K.1.1.1
Baseplate structural protein complex (GP5 is a lysozyme showing limited similarity to ComA of Neisseria species (3.A.11.2.1)) plus Gp18 tail sheath protein of phage T4. Gp5 (575 aas), the baseplate hub subunit, contains (1) an N-terminal GP5_OB domain, (2) a central lysozyme domain, and (3) a C-terminal domain of ~200 aas with repeat units that resemble BigA (1.B.12.5.5; residues 400-600) and ComA (3.A.11.2.1; residues 400-600). Twenty proteins comprise the entire tail complex of T4. See Rossmann et al. 2004 and Leiman et al. 2010) for tabulation of the properties and evidence concerning the functions of these constituents. gp27 and gp29 may comprise the transmembrane channel (Hu et al. 2015). The tail complex of T4 resembles the type VI protein secretion systems (TC# 3.A.23) of enteric bacteria (Shneider et al. 2013).