The WX100 protein super-family consists of three subfamilies (A). Besides the nearly 100 % conserved WXG motif, there is a highly conserved sequence pattern at the C-termini of the proteins (A/B). The reported proteins that are mutually dependently secreted with CFP-10/ESAT-6 share the same C-terminal conserved residue pattern (C). The side chains of these C-terminal amino acids all decorate the same side of the terminal -helix (D). This sequence pattern is common to all WXG100 proteins and therefore we believe it to represent the secretion signal for all substrates of T7SS/b. (Figure taken from Poulsen 2014)