Virulence regulator that has both architectural and regulatory roles. Impacts cell wall functions and pathogenesis through regulation of multiple genes, including the espACD operon, which is a key ESX-1 component. Influences target gene expression positively or negatively, depending on its binding position relative to the genes it controls. Acts by binding directly to the DNA. May play a central role in regulating virulence gene expression. Homodimer. Binds DNA as a dimer of dimers. Negatively autoregulated (PubMed:22479184). Transcriptionally regulated by the MprB/MprA and PhoP/PhoR two-component systems (PubMed:25536998). Expression is growth phase-dependent, peaking in the stationary phase (PubMed:22479184). Probably induced upon phagocytosis (PubMed:18685700). The N-terminal domain binds DNA and the C-terminal domain is involved in dimerization. Both domains are required for transcriptional activity and for ESX-1 function. Mutants exhibit growth defect during infection of mice. They establish a stable infection by three weeks, but the bacterial burden is an order of magnitude less than the wild-type. Was originally thought to be secreted via the ESX-1 secretion system, but it was probably released in the medium via cell lysis.