1sgk

NUCLEOTIDE-FREE DIPHTHERIA TOXIN

spinqualitylabelsall models 1sgk, resolution 2.30Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1sgk is a 1 chain structure with sequence from Corynephage beta. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Activity: NAD(+)--diphthamide ADP-ribosyltransferase, with EC number 2.4.2.36 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [DTX_CORBE] Diphtheria toxin, produced by a phage infecting Corynebacterium diphtheriae, is a proenzyme that, after activation, catalyzes the covalent attachment of the ADP ribose moiety of NAD to eukaryotic elongation factor 2 (eEF-2). Fragment A is the catalytic portion responsible for enzymatic ADP-ribosylation of elongation factor 2, while fragment B is responsible for binding of toxin to cell receptors and entry of fragment A. Publication Abstract from PubMed The crystal structure of diphtheria toxin (DT) in the absence of nucleotide (nucleotide-free DT) has been determined at 2.3 A resolution to a crystallographic R factor and free R factor of 18.2 and 28.2%, respectively. A comparison of this structure to the previously determined structures of DT in complex with adenyly(3'-5')uridine monophosphate (ApUp) and DT in complex with nicotinamide adenine dinucleotide (NAD) reveals that there are no significant movements of the two subdomains of the catalytic (C) domain associated with dinucleotide binding. The side chains of six residues within the active-site cleft, including Tyr65, Pro38, Tyr27, Thr23, Glu148, and Tyr54, show movements of up to 3 A upon dinucleotide binding. In the structure of nucleotide-free DT, the active-site loop residues 39-47 of the C domain are well ordered and extend over the active-site cleft in approximately the same position as in the structure of DT in complex with ApUp. This is in contrast to the structure of the DT-NAD complex, in which the active-site loop is disordered. On the basis of a comparison of the nucleotide-free and NAD-bound DT structures, we suggest that the interaction of NAD with Pro38 and also possibly Tyr54 and Trp153 could disrupt the network of hydrogen bonds that stabilizes the position of the active-site loop over the active-site cleft, allowing this loop to become disordered. This may be an important step in binding of the C domain of DT to its substrate, elongation factor-2. Crystal structure of nucleotide-free diphtheria toxin.,Bell CE, Eisenberg D Biochemistry. 1997 Jan 21;36(3):481-8. PMID:9012663 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Diphtheria toxin

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