1XTC	Toxin	date	Jan 10, 1996
title	Cholera Toxin
authors	R.-G.Zhang, E.Westbrook
compound		source
Molecule: Cholera Toxin Chain: A, C, D, E, E, F, G, H Synonym: Ctx, Choleragen		Organism_scientific: Vibrio Cholerae Organism_common: Vibrio Strain: 569b Other_details: Commercially Obtained From List Biological Laboratory, Campber Ca95008
symmetry	Space Group: P 1 21 1	R_factor	0.185
crystal cell	length a length b length c angle alpha angle beta angle gamma 73.000 92.200 60.600 90.00 106.40 90.00
method	X-Ray Diffraction	resolution	2.4 Å
note	1XTC (Molecule of the Month:pdb69)
domain	The four c-terminal residues of the a2 chain occupy the central pore of the holotoxin. Deletion of this residues weakens the interaction between the a subunit and the b pentamer whithout impairing the pentamer formation.
similarity	Belongs to the Enterotoxin_b family.
subunit	The a subunit contains two chains, a1 and a2, linked by a disulfide bridge. The holotoxin (choleragen) consists of a pentameric ring of b subunits whose central pore is occupied by the a subunit.
catalytic activ.	Nad(+) + peptide diphthamide = nicotinamide + peptide n-(adp-d-ribosyl)diphthamide.
genes	ctxA, ctxB (V. cholerae)
function	This leads to an overproduction of camp and eventually to a hypersecretion of chloride and bicarbonate followed by water, resulting in the characteristic cholera stool. The a2 chain tethers a1 to the pentameric ring. The a1 chain catalyzes the adp-ribosylation of gs alpha, a gtp-binding regulatory protein, to activate the adenylate cyclase. It can bind five gm1 gangliosides. The b subunit pentameric ring directs the a subunit to its target by binding to the gm1 gangliosides present on the surface of the intestinal epithelial cells. It has no toxic activity by itself.
Gene Ontology	Chain Function Process Component A, C catalytic activity transferase activity transferase activity, transf... NAD+-diphthamide ADP-ribosyl... pathogenesis extracellular region H, F, D, G, E pathogenesis extracellular region membrane
Primary reference	The three-dimensional crystal structure of cholera toxin., Zhang RG, Scott DL, Westbrook ML, Nance S, Spangler BD, Shipley GG, Westbrook EM, J Mol Biol 1995 Aug 25;251(4):563-73. PMID:7658473

Data retrieval

Asymmetric unit, PDB entry: [header only] [complete with coordinates] (140 Kb) [Save to disk] Biological Unit Coordinates (1xtc.pdb1.gz) 122 Kb CSU: Contacts of Structural Units for 1XTC Likely Quarternary Molecular Structure file(s) for 1XTC Retrieve 1XTC in mmCIF format [Save to disk]

View 1XTC in 3D

On Jmol, a nice Rasmol like molecule viewer. This is good for easiest viewing of basic structure. On FirstGlance, an excellent tool for a guided tour on the structure components, by E. Martz. On AstexViewer, from MSD-EBI (viewer documentation). On RasMol (Install RasMol freeware) Here's help on how to use RasMol.

Visual 3D analysis of 1XTC

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Structure-derived information

Dipole moment, from Dipole Server at Weizmann Institute Crystal Contacts, from CryCo at Weizmann Institute 3D motif for 1XTC, from MSDmotif at EBI Genome occurence of 1XTC's fold from GeneCensus Classification of representative domains in scop (Structural Classification of Proteins)     - Domain d1xtc.1, region A:,C [Jmol] [rasmolscript] [script source]     - Domain d1xtcd_, region D [Jmol] [rasmolscript] [script source]     - Domain d1xtce_, region E [Jmol] [rasmolscript] [script source]     - Domain d1xtcf_, region F [Jmol] [rasmolscript] [script source]     - Domain d1xtcg_, region G [Jmol] [rasmolscript] [script source]     - Domain d1xtch_, region H [Jmol] [rasmolscript] [script source] Fold representative 1xtc from FSSP and Dali (Families of Structurally Similar Proteins) Class (fold), Architecture (subfold), Topology, Homologous superfamily from CATH Summaries and structural analyses of PDB data files from PDBSum Identification of Protein Pockets & Cavities at CASTp

Sequence-derived information

View one-letter amino acid or nucleotide sequence for each chain: [1xtc_F] [1xtc_E] [1xtc_G] [1xtc_C] [1xtc_A] [1xtc_H] [1xtc_D]

Other resources with information on 1XTC

InterPro: IPR001144 , IPR001835 PDBREPORT (protein verification by WHAT_CHECK procedures) MMDB (Entrez's Structure Database)

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