Component of the type VII secretion system (Ess). Provides together with EssB and other components such as EssC and EssE a secretion plateform accross the cytoplasmic membrane in the host. Homodimer (By similarity). Interacts with EssB (PubMed:29737367, PubMed:28874412). Deletion abrogates the secretion of EsxA and EsxC into the extracellular medium. Belongs to the EsaA family.