PDBsum entry 1b44

Toxin

PDB id: 1b44

Contents

Protein chains

106 a.a.

PDB id:

1b44

Name:

Toxin

Title:

Crystal structure of the b subunit of heat-labile enterotoxin from e. Coli carrying a peptide with anti-hsv activity

Structure:

Protein (b-pol subunit of heat-labile enterotoxin). Chain: d, e, f, g, h. Fragment: subunit b. Synonym: etb-pol. Engineered: yes. Other_details: the b subunit has a peptide with anti-hsv activity as an extension.

Source:

Escherichia coli. Organism_taxid: 562. Expressed in: vibrio cholerae. Expression_system_taxid: 666. Other_details: the protein was cloned and expressed in vibrio cholera

Biol. unit:

Pentamer (from PQS)

Resolution:

3.30Å R-factor: 0.212 R-free: 0.255

Authors:

D.Matkovic-Calogovic,A.Loregian,M.R.D'Acunto,R.Battistutta,A.Tossi, G.Palu,G.Zanotti

Key ref:

D.Matković-Calogović et al. (1999). Crystal structure of the B subunit of Escherichia coli heat-labile enterotoxin carrying peptides with anti-herpes simplex virus type 1 activity. J Biol Chem, 274, 8764-8769. PubMed id: 10085117

Date:

04-Jan-99 Release date: 13-Jan-99

Protein chains

P0CK94  (ELBH_ECOLX) -  Heat-labile enterotoxin B chain from Escherichia coli

Seq: 124 a.a.

Struc: 106 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

J Biol Chem 274:8764-8769 (1999)

PubMed id: 10085117

Crystal structure of the B subunit of Escherichia coli heat-labile enterotoxin carrying peptides with anti-herpes simplex virus type 1 activity.

D.Matković-Calogović, A.Loregian, M.R.D'Acunto, R.Battistutta, A.Tossi, G.Palù, G.Zanotti.

ABSTRACT

Two chimeric proteins, consisting of the B subunit of Escherichia coli heat-labile enterotoxin with different peptides fused to the COOH-terminal ends, have been crystallized and their three-dimensional structure determined. The two extensions correspond to (a) a nonapeptide representing the COOH-terminal sequence of the small subunit of herpes simplex virus type 1 ribonucleotide reductase and (b) a 27-amino acid long peptide, corresponding to the COOH-terminal end of the catalytic subunit (POL) of DNA polymerase from the same virus. Both proteins crystallize in the P41212 space group with one pentameric molecule per asymmetric unit, corresponding to a solvent content of about 75%. The overall conformation of the B subunit pentamer in the two chimeric proteins, which consists of five identical polypeptide chains, is very similar to that in the native AB complex and conforms strictly to 5-fold symmetry. On the contrary, the peptide extensions are essentially disordered: in the case of the nonapeptide, only 5 and 6 amino acids were, respectively, positioned in two monomers, while in the other three only 2 residues are ordered. The extension is fully confined to the surface of the pentamer opposite to the face that interacts with the membrane and consequently it does not interfere with the ability of the B subunit to interact with membrane receptors. Moreover, the conformational flexibility of the two peptide extensions could be correlated to their propensity for proteolytic processing and consequent release of a biologically active molecule into cultured cells.

Selected figure(s)

Figure 2.
Fig. 2. Schematic drawing of the overall structure of the EtxB-R2 pentamer, prepared with the MOLSCRIPT program (37). The portion of peptide extensions visible in the electron density map are in black. Arrows indicate the loop 54-61. The amino acid sequences of COOH terminus of the two fusion proteins, from residue 102, are (peptide extensions in bold letters): EtxB-R2, ... Glu-Lys-Leu-Tyr-Ala-Gly-Ala-Val-Val-Asn-Asp-Leu; EtxB-Pol, ... Glu-Lys-Leu-Ala-Gly-Phe-Gly-Ala-Val-Gly-Ala-Gly-Ala-Thr-Ala-Glu-Glu-Thr-Arg-Arg-Met-Leu-His-Arg-Ala-Phe-Asp-Thr-Leu-Ala.

Figure 4.
Fig. 4. Stereo drawing of the C chain trace of the EtxB-R2 subunit, with all the atoms superimposed for each extension: amino acids from 103 to 108 in chain D, from 103 to 109 in chain F, from 103 to 105 in chains E, G, and H. The five sulfate ions close to Lys^103 are also shown.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (1999, 274, 8764-8769) copyright 1999.

Figures were selected by an automated process.