Homologous Superfamily

Diphtheria toxin, receptor-binding domain superfamily (IPR036799)

Short name: Diphtheria_tox_rcpt-bd_dom_sf

Overlapping entries


This entry represents the C-terminal receptor-binding domain (also known as the R domain) of Diphtheria toxin. This domain has a beta-sandwich fold consisting of nine strands in two sheet with greek-key topology; it is a subclass of immunoglobin-like fold [PMID: 9012663]. The R domain binds to cell surface receptor, permitting the toxin to enter the cell by receptor mediated endocytosis [PMID: 7833808, PMID: 8573568].

Diphtheria toxin (EC: is a 58 kDa protein secreted by lysogenic strains of Corynebacterium diphtheriae. The toxin causes the disease diphtheria in humans by gaining entry into the cell cytoplasm and inhibiting protein synthesis [PMID: 8573568]. The mechanism of inhibition involves transfer of the ADP-ribose group of NAD to elongation factor-2 (EF-2), rendering EF-2 inactive. The catalysed reaction is as follows: NAD+ + peptide diphthamide = nicotinamide + peptide N-(ADP-D-ribosyl)diphthamide

The crystal structure of the diphtheria toxin homodimer has been determined to 2.5A resolution [PMID: 1589020]. The structure reveals a Y-shaped molecule of 3 domains, a catalytic domain (fragment A), whose fold is of the alpha + beta type; a transmembrane (TM) domain, which consists of 9 alpha-helices, 2 pairs of which may participate in pH-triggered membrane insertion and translocation; and a receptor-binding domain, which forms a flattened beta-barrel with a jelly-roll-like topology [PMID: 1589020]. The TM- and receptor binding-domains together constitute fragment B.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.