AB5 toxin

AB5 toxin

The AB5 (or AB5) toxins are six-component protein complexes secreted by a number of pathogenic bacteria. All share a similar structure and mechanism for entering targeted host cells.cite journal |author = Merritt E, Hol W |title=AB5 toxins |journal=Curr Opin Struct Biol |volume=5 |issue=2 |pages=165–71 |year=1995 |pmid=7648317 |doi=10.1016/0959-440X(95)80071-9]

Structure and mechanism

A complete AB5 toxin complex contains six protein units. Five – the B subunits – are similar or identical in structure; the remaining A subunit is unique.

The A subunit (or a portion thereof) of an AB5 toxin is the portion of the complex responsible for toxicity. Typically it will have enzymatic activity inside the host cell.

The B subunits form a pentameric (five-membered) ring, into which one end of the A subunit extends and is held. This B subunit ring is also capable of binding to a receptor on the surface of the host cell.cite journal |author=Lencer W, Saslowsky D |title=Raft trafficking of AB5 subunit bacterial toxins |journal=Biochim Biophys Acta |volume=1746 |issue=3 |pages=314–21 |year=2005 |pmid=16153723 |doi=10.1016/j.bbamcr.2005.07.007] (Without the B subunits, the A subunit has no way of attaching to or entering the cell, and thus no way to exert its toxic effect.)

List of AB5 toxins

*"Campylobacter jejuni" enterotoxin (from "Campylobacter jejuni")
*cholera toxin ("Vibrio cholerae")
*heat-labile enterotoxins (LT and LT-II) ("Escherichia coli")
*pertussis toxin ("Bordetella pertussis")
*shiga toxin ("Shigella dysenteriae")
*shiga-like toxin (or "verotoxin") (enterohemorrhagic varieties of "E. coli" including )


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