Forms a tight 1:1 complex with EsxV. The complex is destabilized at low pH. Unfolding of the proteins is required for dissociation of the complex and membrane binding. Probably secreted via the ESX-5 / type VII secretion system (T7SS) (Probable). May bind to lipid membranes after dissociation of the complex (Probable). Belongs to the WXG100 family. CFP-10 subfamily.