Required for YukE secretion. Probable component or regulator of the ESX/ESAT-6-like secretion system (BsEss) (PubMed:23861817, PubMed:24798022). Bacteriophage SPP1 receptor. Essential for the irreversible adsorption of the bacteriophage (PubMed:15576783). Cells lacking this gene are blocked in YukE secretion. Belongs to the EsaA family.