Component of the type VII secretion system (Ess). Required for the secretion of substrates including EsxA and EsxB (PubMed:15657139). However, unable to support secretion of the substrate protein EsxC (By similarity). Homooligomer. Interacts with EsaE. Mutations abolish synthesis and secretion of both EsxA and EsxB, without affecting their transcription. Mutant shows a significant reduction in the ability to establish kidney or liver abscesses in infected mice. Belongs to the EssC family.