This entry represents a domain found in actinobacterial proteins, including EspA and EspE from Mycobacteria.The ESX-1 operon is present in a number of Mycobacteria strains []. In Mycobacterium tuberculosis (Mtb) the type VII ESX-1 secretion apparatus is used to translocate the key virulence factors EsxA (ESAT-6) and EsxB (CFP-10). In Mtb, the EspA protein is encoded by the unlinked espACD operon []. The EspA protein of Mycobacterium tuberculosis is essential for the type VII ESX-1 protein secretion apparatus []. EspA, ESAT-6, and CFP-10 are each critical for virulence of pathogenic mycobacteria and secretion of these three proteins, is mutually dependent [, ]. EspA undergoes Cys138-mediated homodimerization, although the process is not required for EspA or ESAT-6 secretion []. EspE is encoded by the ESX-1 operon []. In M. smegmatis it has been shown to colocalise with SaeC at, or near, the cell pole []. In M. smegmatis secretion of the heterodimer of EsxAB (ESAT-6/CFP-10) is dependent on the co-secretion of proteins encoded from both esx1 (eg., EspE) and non-esx1 genes (eg., EspA) [].
