Protein Domain : Diphtheria toxin, translocation domain superfamily IPR036801

Type	Homologous_superfamily
Description	Diphtheria toxin ( ) is a 58kDa 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 [ ]. 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 []. The structure reveals a Y-shaped molecule of 3 domains, a catalytic domain (fragment A), whose fold is of the α+β type; a transmembrane (TM) domain, which consists of 9 α-helices, 2 pairs of which may participate in pH-triggered membrane insertion and translocation; and a receptor-binding domain, which forms a flattened β-barrel with a jelly-roll-like topology []. The TM- and receptor binding-domains together constitute fragment B.This entry represents the translocation domain (also known as the T domain) found in the middle of the Diphtheria toxin protein. The T domain has a multi-helical globin-like fold with two additional helices at N-termini, but which has no counterpart to the first globin helix. This domain is thought to unfold in the membrane [ ]. pH-induced conformational change in the T domain triggers insertion into the endosomal membrane and facilitates the transfer of the catalytic domain into the cytoplasm [, ].
Short Name	Diphtheria_tox_transloc_sf