Required to deliver LXG toxins to target cells. Homodimer. Secreted via the ESX/ESAT-6-like secretion system (BsEss) / type VII secretion system (T7SS) (PubMed:23861817, PubMed:24798022). Can be secreted as a dimer (PubMed:24828531). Positively regulated by phosphorylated DegU. The WXG motif and the C-terminal tail are crucial for secretion. Cells lacking this gene display an increased bacteriophage SPP1 resistance phenotype (PubMed:15576783). Loss of delivery of LXG type toxins to target cells (PubMed:34280190). Belongs to the WXG100 family. sagEsxA-like subfamily. Extended N-terminus.