The WXG100 protein secretion system (Wss) is responsible for the secretion of WXG100 proteins (Pfam:PF06013) such as ESAT-6 and CFP-10 in Mycobacterium tuberculosis or EsxA and EsxB in Staphylococcus aureus. In S. aureus, the Wss seems to be encoded by a locus of eight CDS, called ess (eSAT-6 secretion system). This locus encodes, amongst several other proteins, EssA, a protein predicted to possess one transmembrane domain. Due to its predicted membrane location and its absolute requirement for WXG100 protein secretion, it has been speculated that EssA could form a secretion apparatus in conjunction with the polytopic membrane protein EsaA, YukC (Pfam:PF10140) and YukAB, which is a membrane-bound ATPase containing Ftsk/SpoIIIE domains (Pfam:PF01580) called EssC in S. aureus and Snm1/Snm2 in Mycobacterium tuberculosis. Proteins homologous to EssA, YukC, EsaA and YukD seem absent from mycobacteria [1].

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2: EsxA and EsxB are secreted by an ESAT-6-like system that is required for the pathogenesis of Staphylococcus aureus infections. Burts ML, Williams WA, DeBord K, Missiakas DM; Proc Natl Acad Sci U S A. 2005;102:1169-1174. PMID:15657139

3: Outer membrane translocation: numerical protein secretion nomenclature in question in mycobacteria. Desvaux M, Hebraud M, Talon R, Henderson IR; Trends Microbiol. 2009;17:338-340. PMID:19674902

4: New insights into the distribution of WXG100 protein secretion systems. Sutcliffe IC; Antonie Van Leeuwenhoek. 2011;99:127-131. PMID:20852931

5: Secretion and subcellular localizations of bacterial proteins: a semantic awareness issue. Desvaux M, Hebraud M, Talon R, Henderson IR; Trends Microbiol. 2009;17:139-145. PMID:19299134