6 kDa early secretory antigenic target - P9WNK7 (ESXA_MYCTU)


Protein Feature View of PDB entries mapped to a UniProtKB sequence  

  • Number of PDB entries for P9WNK7: 2
A secreted protein that plays a number of roles in modulating the host's immune response to infection as well as being responsible for bacterial escape into the host cytoplasm. Acts as a strong host (human) T-cell antigen (PubMed:7729876, PubMed:11940590). Inhibits IL-12 p40 (IL12B) and TNF-alpha expression by infected host (mouse) macrophages, reduces the nitric oxide response by about 75% (PubMed:14557536). In mice previously exposed to the bacterium, elicits high level of IFN-gamma production by T-cells upon subsequent challenge by M.tuberculosis, in the first phase of a protective immune response (PubMed:7897219, PubMed:7729876). Higher levels (1.6-3.3 uM) of recombinant protein inhibit IFN-gamma production by host (human) T-cells and also IL-17 and TNF-alpha production but not IL-2; decreases expression of host ATF-2 and JUN transcription factors by affecting T-cell receptors signaling downstream of ZAP70, without cytotoxicity or apoptosis (PubMed:19265145). EsxA inhibits IFN-gamma production in human T-cells by activating p38 MAPK (MAPK14), p38 MAPK is not responsible for IL-17 decrease (PubMed:21586573). Binds host (mouse) Toll-like receptor 2 (TLR2) and decreases host MYD88-dependent signaling; binding to TLR2 activates host kinase AKT and subsequently inhibits downstream activation of NF-kappa-B; the C-terminal 20 residues (76-95) are necessary and sufficient for the TLR2 inhibitory effect (PubMed:17486091). Required for induction of host (human) IL-1B maturation and release by activating the host NLRP3/ASC inflammasome; may also promote access of other tuberculosis proteins to the host cells cytoplasm (PubMed:20148899). Induces IL-8 (CXCL8) expression in host (human) lung epithelial cells (PubMed:23867456). Exogenously applied protein, or protein expressed in host (human and mouse), binds beta-2-microglobulin (B2M) and decreases its export to the cell surface, probably leading to defects in class I antigen presentation by the host cell (PubMed:25356553). Responsible for mitochondrial fragmention, redistribution around the cell nucleus and decreased mitochondrial mass; this effect is not seen until 48 hours post-infection (PubMed:26092385). Able to disrupt artificial planar bilayers in the absence of EsxB (CFP-10) (PubMed:14557547). Native protein binds artificial liposomes in the absence but not presence of EsxB and is able to rigidify and lyse them; the EsxA-EsxB complex dissociates at acidic pH, EsxB might serve as a chaperone to prevent membrane lysis (PubMed:17557817). Recombinant protein induces leakage of phosphocholine liposomes at acidic pH in the absence of ExsB, undergoes conformational change, becoming more alpha-helical at acidic pH (PubMed:23150662, PubMed:25645924). The study using recombinant protein did not find dissociation of EsxA-EsxB complex at acidic pH (PubMed:23150662). Involved in translocation of bacteria from the host (human) phagolysosome to the host cytoplasm (PubMed:17604718, PubMed:22319448). Translocation into host cytoplasm is visible 3 days post-infection using cultured human cells and precedes host cell death (PubMed:22319448). Recombinant protein induces apoptosis in host (human) differentiated cell lines, which is cell-line dependent; bacteria missing the ESX-1 locus do not induce apoptosis (PubMed:17298391). Host (human) cells treated with EsxA become permeable to extracellular dye (PubMed:17298391). EsxA and EsxA-EsxB are cytotoxic to pneumocytes (PubMed:19906174). ESX-1 secretion system-induced host (mouse) cell apoptosis, which is probably responsible for infection of new host cells, might be due to EsxA (PubMed:23848406). EsxA induces necrosis in aged neutrophils (PubMed:25321481). May help regulate assembly and function of the type VII secretion system (T7SS) (By similarity). EsxA disassembles pre-formed EccC-EsxB multimers, possibly by making EccC-EsxA-EsxB trimers instead of EccC-EsxB-EsxB-EccC tetramers. UniProt
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Subunit Structure
Forms a tight 1:1 complex with EsxB (CFP-10) (PubMed:11940590, PubMed:14557536, PubMed:16048998, PubMed:16973880, PubMed:19854905, PubMed:19906174, PubMed:23150662, PubMed:26260636, PubMed:20085764, PubMed:15973432, PubMed:24586681). The complex persists even after secretion (PubMed:16048998). Recombinant His-tagged protein forms dimers and higher order multimers; how the protein is prepared influences its multimerization and its subsequent properties in vitro (PubMed:26260636). In vitro EsxB only interacts with non-acetylated EsxA; it also interacts with C-terminally truncated EsxA (missing the last 10 residues) (PubMed:15378760). The native EsxA-EsxB complex dissociates at pH 4.0, and EsxA may then be freed to lyse (host) membranes (PubMed:17557817). Another study using recombinant protein did not find dissociation at acidic pH (PubMed:23150662). Recombinant heterodimer (with a His tag on EsxB) can be dissociated by the detergents amidosulfobetaine-14 and lauryldimethylamine N-oxide (PubMed:26260636). Interacts with EspF (PubMed:19682254). An artificial EsxB-EsxA heterodimer interacts with EspA, EccB1, EccCa1, EccCb1, EspI, EspJ, EccA2 and EccE2; the latter 2 are from the adjacent ESX-2 locus (PubMed:19854905). Contributes to the heterodimer's interaction with EccCb1 (PubMed:19854905). Interacts with host (mouse and human) TLR2 (PubMed:17486091, PubMed:20800577). Interacts with host (human) beta-2-microglobulin (B2M) alone and in complex with EsxB; only binds free B2M and not B2M in complex with HLA-I (PubMed:25356553). The EsxA-EsxB-B2M complex can be detected in the host endoplasmic reticulum (PubMed:25356553). The B2M-EsxA complex can be detected in patients with pleural tuberculosis and is stable from pH 4.0 to 8.0 and in the presence of 2M NaCl (PubMed:25356553). UniProt
May be secreted as a 4 coiled-coil complex with EsxB (PubMed:16048998). UniProt
  • Other Gene names: esxA, esaT6, Rv3875, MTV027.10
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