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Publication Abstract from PubMed

AB5 toxins are composed of an enzymatic A subunit that disrupts cellular function associated with a pentameric B subunit required for host cell invasion. EcxAB is an AB5 toxin isolated from clinical strains of Escherichia coli classified as part of the cholera family due to B subunit homology. Cholera-group toxins have catalytic ADP-ribosyltransferases as their A subunits, so it was surprising that EcxA did not. We confirmed that EcxAB self-associates as a functional toxin and obtained its structure. EcxAB is a prototypical member of a hybrid AB5 toxin family containing metzincin-type metalloproteases as their active A subunit paired to a cholera-like B subunit. Furthermore, EcxA is distinct from previously characterized proteases and thus founds an AB5-associated metzincin family that we term the toxilysins. EcxAB provides the first observation of conserved B subunit usage across different AB5 toxin families and provides evidence that the intersubunit interface of these toxins is far more permissive than previously supposed.

EcxAB Is a Founding Member of a New Family of Metalloprotease AB Toxins with a Hybrid Cholera-like B Subunit.,Ng NM, Littler DR, Paton AW, Le Nours J, Rossjohn J, Paton JC, Beddoe T Structure. 2013 Oct 1. pii: S0969-2126(13)00345-6. doi:, 10.1016/j.str.2013.08.024. PMID:24095060^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.