Part of the ESX specialized secretion system, which exports proteins from the cell including EsxA (ESAT-6) and EsxB (CFP-10) (PubMed:25865481). Has weak intrinsic ATPase activity; probably only the first FtsK domain can hydrolyze ATP (PubMed:25865481). Might be the translocase subunit (PubMed:25865481). EsxB binding to the third FtsK domain causes multimerization; a subsequent unknown step relieves the allosteric inhibition of linker 2 on FtsK domain 1, activating the ATPase activity; a mutant EsxB ('Ala-98') does not cause multimers to form (PubMed:25865481). The cytosolic domain can form homodimers (PubMed:25865481). Binds EsxB, which leads to multimerization, however EsxA disassembles the multimers, possibly by making EccC-EsxA-EsxB trimers instead of EccC-EsxB-EsxB-EccC tetramers. Forms a complex with EsxA and EsxB, probably wholly mediated by EsxB (PubMed:25865481). The cytoplasmic domain is a rigid structure with 4 domains (residues 276 to 401 form an unnamed domain) plus the 3 FtsK (ATPase) domains which are connected by short linkers. Binds EsxB via a small pocket (residues 1163-1208) in the third FtsK (ATPase) domain; the linkers between FtsK 1-2 and FtsK 2-3 bind in an analogous manner to FtsK 1 and FtsK 2. Linker 2 binding to FtsK 1 decreases its ATPase activity and probably controls it (PubMed:25865481). Unlike the well characterized M.tuberculosis ESX-1 cluster, this protein is not split into 2 genes. This subunit and a WGX100 family protein are the only proteins universally associated with T7SS.