PDBsum entry 1fgb

Enterotoxin

PDB id: 1fgb

Contents

Protein chains

103 a.a.

Waters ×204

PDB id:

1fgb

Name:

Enterotoxin

Title:

Toxin

Structure:

Cholera toxin b subunit pentamer. Chain: d, e, f, g, h. Synonym: choleragenoid

Source:

Vibrio cholerae. Organism_taxid: 44104. Strain: 569b

Biol. unit:

Pentamer (from PQS)

Resolution:

2.40Å R-factor: 0.171

Authors:

R.-G.Zhang,E.Westbrook

Key ref:

R.G.Zhang et al. (1995). The 2.4 A crystal structure of cholera toxin B subunit pentamer: choleragenoid. J Mol Biol, 251, 550-562. PubMed id: 7658472 DOI: 10.1006/jmbi.1995.0455

Date:

21-Feb-96 Release date: 23-Dec-96

Protein chains

P01556  (CHTB_VIBCH) -  Cholera enterotoxin subunit B from Vibrio cholerae serotype O1 (strain ATCC 39315 / El Tor Inaba N16961)

Seq: 124 a.a.

Struc: 103 a.a.*

* PDB and UniProt seqs differ at 2 residue positions (black crosses)

DOI no: 10.1006/jmbi.1995.0455

J Mol Biol 251:550-562 (1995)

PubMed id: 7658472

The 2.4 A crystal structure of cholera toxin B subunit pentamer: choleragenoid.

R.G.Zhang, M.L.Westbrook, E.M.Westbrook, D.L.Scott, Z.Otwinowski, P.R.Maulik, R.A.Reed, G.G.Shipley.

ABSTRACT

Cholera toxin, a heterohexameric AB5 enterotoxin released by Vibrio cholera, induces a profuse secretory diarrhea in susceptible hosts. Choleragenoid, the B subunit pentamer of cholera toxin, directs the enzymatic A subunit to its target by binding the GM1 gangliosides exposed on the luminal surface of intestinal epithelial cells. The crystal structure of choleragenoid has been independently solved and refined at 2.4 A resolution by combining single isomorphous replacement with non-crystallographic symmetry averaging. The structure of the B subunits, and their pentameric arrangement, closely resembles that reported for the intact holotoxin, choleragen, the heat-labile enterotoxin from Escherichia coli, and for a choleragenoid-GM1 pentasaccharide complex. In the absence of the A subunit the central cavity of the B pentamer is a highly solvated channel. The binding of choleragenoid to the A subunit or to its receptor pentasaccharide modestly affects the local stereochemistry without perceptibly altering the subunit interface.

Selected figure(s)

Figure 1.
Figure 1. Overview of the crystalline choleragenoid. A, Stereo pair of the pentamer viewed from the ``side'' (along an axis perpendicular to the 5-fold axis). Each subunit is colored differently with only the side-chains of Tyr12, Gln56, and Trp88 shown (green). These residues surround the GM1-binding sites located adjacent to the ``ventral'' flange of choleragenoid. The A subunit of the holotoxin lies on top of the ``dorsal'' surface. The disulfide bridges between residues 9 and 86 are colored magenta. The amino and carboxyl termini are shown as blue and red spheres, respectively. B, Stereo pair of the pentamer viewed from the ``ventral'' surface (along an axis parallel to the 5-fold). Residues are indicated as in A. The central pore of choleragen is occupied by the helical terminus of the A2 chain in the holotoxin (Zhang et al., 1995).

Figure 7.
Figure 7. The central pore of choleragenoid and choleragen. Cross-section through the central pore of (A) choleragenoid, and (B) choleragen (Zhang et al., 1995) along the 5-fold axis. For clarity, only the side-chains of the central a-helices are shown (magenta). Solvent molecules are indicates as yellow spheres. The carboxyl end of the A2 chain (gold) occupies the central pore of choleragen. Part of the A1 chain (cyan) is also shown in B for orientation purposes. In the absence of the A2 chain, the pore is a highly solvated channel. The location of the ganglioside-binding site is indicated by the side-chain of Trp88 (green).

The above figures are reprinted by permission from Elsevier: J Mol Biol (1995, 251, 550-562) copyright 1995.

Figures were selected by an automated process.