Part of the ESX-1 specialized secretion system, which delivers several virulence factors to host cells during infection, including the key virulence factors EsxA (ESAT-6) and EsxB (CFP-10). Possibly a homodimer (PubMed:26922638). Part of the ESX-1 / type VII secretion system (T7SS), which is composed of cytosolic and membrane components. The ESX-1 membrane complex is composed of EccB1, EccCa1, EccCb1, EccD1 and EccE1. Double espI-eccD1 mutants abolish EsxA and EsxB secretion, but not their expression (PubMed:14557547). Disruption abolishes EsxA and EsxB secretion, but not their expression (PubMed:14557536). Results in a lack of antigen specific immunogenicity and leads to attenuated virulence (PubMed:16368961). Mutants exhibit defects in bacterial growth during the acute phase of C57BL/6 mouse infection, but survive for 140 days despite a wild-type bacterial load in the lungs at 100 days post-infection, suggesting the pathway is required for virulence (PubMed:14557536). Nearly wild-type levels of IL-12 p40 (IL12B) and TNF-alpha are produced by infected murine macrophages, while the nitric oxide response is about 50% reduced (PubMed:14557536). Mouse macrophages do not induce cGAMP production, and thus do not sense bacterial DNA correctly to induce the innate immune response (PubMed:26048137). The structure in 4KV3 was determined for a fusion protein with E.coli maltose-binding protein. Belongs to the EccD/Snm4 family.