Protein: Toxin B (EC 3.4.22.-) [Cleaved into: Glucosyltransferase TcdB (EC 2.4.1.-)] (P18177)
Organism: Clostridioides difficile (Peptoclostridium difficile)
Function: Precursor of a cytotoxin that targets and disrupts the colonic epithelium, inducing the host inflammatory and innate immune responses and resulting in diarrhea and pseudomembranous colitis. TcdB constitutes the main toxin that mediates the pathology of C.difficile infection, an opportunistic pathogen that colonizes the colon when the normal gut microbiome is disrupted. Compared to TcdA, TcdB is more virulent and more important for inducing the host inflammatory and innate immune responses. This form constitutes the precursor of the toxin: it enters into host cells and mediates autoprocessing to release the active toxin (Glucosyltransferase TcdB) into the host cytosol. Targets colonic epithelia by binding to the frizzled receptors FZD1, FZD2 and FZD7, and enters host cells via clathrin-mediated endocytosis. Frizzled receptors constitute the major host receptors in the colonic epithelium, but other receptors, such as CSPG4 or NECTIN3/PVRL3, have been identified. Binding to carbohydrates and sulfated glycosaminoglycans on host cell surface also contribute to entry into cells (By similarity). Once entered into host cells, acidification in the endosome promotes the membrane insertion of the translocation region and formation of a pore, leading to translocation of the GT44 and peptidase C80 domains across the endosomal membrane. This activates the peptidase C80 domain and autocatalytic processing, releasing the N-terminal part (Glucosyltransferase TcdB), which constitutes the active part of the toxin, in the cytosol.
Subcellular location: [Toxin B]: Secreted {ECO:0000269|PubMed:22685398}. Host endosome membrane {ECO:0000269|PubMed:11152463, ECO:0000305|PubMed:12941936}. Note=Secreted from C.difficile cell into the extracellular environment via help of holin-like protein TcdE/UtxA (PubMed:22685398). Binds to the cell surface receptors via the receptor-binding region and enters the cells via clathrin-mediated endocytosis (PubMed:20498856). Acidification in the endosome triggers conformational changes that promote the membrane insertion of the translocation region, allowing formation of a pore, leading to translocation of the GT44 and peptidase C80 domains across the endosomal membrane (PubMed:10768933, PubMed:11152463, PubMed:12941936). 1D-myo-inositol hexakisphosphate-binding (InsP6) activates the peptidase C80 domain and autoprocessing, generating the Glucosyltransferase TcdB form, which is released in the host cytosol (PubMed:17334356). {ECO:0000269|PubMed:10768933, ECO:0000269|PubMed:11152463, ECO:0000269|PubMed:12941936, ECO:0000269|PubMed:17334356, ECO:0000269|PubMed:20498856, ECO:0000269|PubMed:22685398}.; SUBCELLULAR LOCATION: [Glucosyltransferase TcdB]: Host cytoplasm, host cytosol {ECO:0000269|PubMed:12941936, ECO:0000269|PubMed:15632438}. Host cell membrane {ECO:0000250|UniProtKB:Q46342}; Peripheral membrane protein {ECO:0000250|UniProtKB:Q46342}; Cytoplasmic side {ECO:0000250|UniProtKB:Q46342}. Note=Binding to phospholipids, such as phosphatidylserine and phosphatidic acid promotes localization to the inner face of the cell membrane close to its membrane anchored substrates (small GTPases). {ECO:0000250|UniProtKB:Q46342}.
Interaction partners:
Sequence:
MSLVNRKQLEKMANVRFRTQEDEYVAILDALEEYHNMSENTVVEKYLKLKDINSLTDIYIDTYKKSGRNKALKKFKEYLVTEVLELKNNNLTPVEKNLHFVWIGGQINDTAINYINQWKDVNSDYNVNVFYDSNAFLINTLKKTVVESAINDTLESFRENLNDPRFDYNKFFRKRMEIIYDKQKNFINYYKAQREENPELIIDDIVKTYLSNEYSKEIDELNTYIEESLNKITQNSGNDVRNFEEFKNGESFNLYEQELVERWNLAAASDILRISALKEIGGMYLDVDMLPGIQPDLFESIEKPSSVTVDFWEMTKLEAIMKYKEYIPEYTSEHFDMLDEEVQSSFESVLASKSDKSEIFSSLGDMEASPLEVKIAFNSKGIINQGLISVKDSYCSNLIVKQIENRYKILNNSLNPAISEDNDFNTTTNTFIDSIMAEANADNGRFMMELGKYLRVGFFPDVKTTINLSGPEAYAAAYQDLLMFKEGSMNIHLIEADLRNFEISKTNISQSTEQEMASLWSFDDARAKAQFEEYKRNYFEGSLGEDDNLDFSQNIVVDKEYLLEKISSLARSSERGYIHYIVQLQGDKISYEAACNLFAKTPYDSVLFQKNIEDSEIAYYYNPGDGEIQEIDKYKIPSIISDRPKIKLTFIGHGKDEFNTDIFAGFDVDSLSTEIEAAIDLAKEDISPKSIEINLLGCNMFSYSINVEETYPGKLLLKVKDKISELMPSISQDSIIVSANQYEVRINSEGRRELLDHSGEWINKEESIIKDISSKEYISFNPKENKITVKSKNLPELSTLLQEIRNNSNSSDIELEEKVMLTECEINVISNIDTQIVEERIEEAKNLTSDSINYIKDEFKLIESISDALCDLKQQNELEDSHFISFEDISETDEGFSIRFINKETGESIFVETEKTIFSEYANHITEEISKIKGTIFDTVNGKLVKKVNLDTTHEVNTLNAAFFIQSLIEYNSSKESLSNLSVAMKVQVYAQLFSTGLNTITDAAKVVELVSTALDETIDLLPTLSEGLPIIATIIDGVSLGAAIKELSETSDPLLRQEIEAKIGIMAVNLTTATTAIITSSLGIASGFSILLVPLAGISAGIPSLVNNELVLRDKATKVVDYFKHVSLVETEGVFTLLDDKIMMPQDDLVISEIDFNNNSIVLGKCEIWRMEGGSGHTVTDDIDHFFSAPSITYREPHLSIYDVLEVQKEELDLSKDLMVLPNAPNRVFAWETGWTPGLRSLENDGTKLLDRIRDNYEGEFYWRYFAFIADALITTLKPRYEDTNIRINLDSNTRSFIVPIITTEYIREKLSYSFYGSGGTYALSLSQYNMGINIELSESDVWIIDVDNVVRDVTIESDKIKKGDLIEGILSTLSIEENKIILNSHEINFSGEVNGSNGFVSLTFSILEGINAIIEVDLLSKSYKLLISGELKILMLNSNHIQQKIDYIGFNSELQKNIPYSFVDSEGKENGFINGSTKEGLFVSELPDVVLISKVYMDDSKPSFGYYSNNLKDVKVITKDNVNILTGYYLKDDIKISLSLTLQDEKTIKLNSVHLDESGVAEILKFMNRKGNTNTSDSLMSFLESMNIKSIFVNFLQSNIKFILDANFIISGTTSIGQFEFICDENDNIQPYFIKFNTLETNYTLYVGNRQNMIVEPNYDLDDSGDISSTVINFSQKYLYGIDSCVNKVVISPNIYTDEINITPVYETNNTYPEVIVLDANYINEKINVNINDLSIRYVWSNDGNDFILMSTSEENKVSQVKIRFVNVFKDKTLANKLSFNFSDKQDVPVSEIILSFTPSYYEDGLIGYDLGLVSLYNEKFYINNFGMMVSGLIYINDSLYYFKPPVNNLITGFVTVGDDKYYFNPINGGAASIGETIIDDKNYYFNQSGVLQTGVFSTEDGFKYFAPANTLDENLEGEAIDFTGKLIIDENIYYFDDNYRGAVEWKELDGEMHYFSPETGKAFKGLNQIGDYKYYFNSDGVMQKGFVSINDNKHYFDDSGVMKVGYTEIDGKHFYFAENGEMQIGVFNTEDGFKYFAHHNEDLGNEEGEEISYSGILNFNNKIYYFDDSFTAVVGWKDLEDGSKYYFDEDTAEAYIGLSLINDGQYYFNDDGIMQVGFVTINDKVFYFSDSGIIESGVQNIDDNYFYIDDNGIVQIGVFDTSDGYKYFAPANTVNDNIYGQAVEYSGLVRVGEDVYYFGETYTIETGWIYDMENESDKYYFNPETKKACKGINLIDDIKYYFDEKGIMRTGLISFENNNYYFNENGEMQFGYINIEDKMFYFGEDGVMQIGVFNTPDGFKYFAHQNTLDENFEGESINYTGWLDLDEKRYYFTDEYIAATGSVIIDGEEYYFDPDTAQLVISE