PDBsum entry 1i4x

Toxin

PDB id: 1i4x

Contents

Protein chain

235 a.a. *

Metals

_ZN

Waters ×91

* Residue conservation analysis

PDB id:

1i4x

Name:

Toxin

Title:

Staphylococcal enterotoxin c2, monoclinic form crystallized at ph 8.0

Structure:

Enterotoxin typE C-2. Chain: a. Synonym: sec2

Source:

Staphylococcus aureus. Organism_taxid: 1280

Resolution:

2.40Å R-factor: 0.207

Authors:

S.Swaminathan,M.Sax

Key ref:

D.Kumaran et al. (2001). Structure of staphylococcal enterotoxin C2 at various pH levels. Acta Crystallogr D Biol Crystallogr, 57, 1270-1275. PubMed id: 11526318 DOI: 10.1107/S0907444901011118

Date:

23-Feb-01 Release date: 14-Mar-01

Protein chain

P34071  (ENTC2_STAAU) -  Enterotoxin type C-2 from Staphylococcus aureus

Seq: 266 a.a.

Struc: 235 a.a.

DOI no: 10.1107/S0907444901011118

Acta Crystallogr D Biol Crystallogr 57:1270-1275 (2001)

PubMed id: 11526318

Structure of staphylococcal enterotoxin C2 at various pH levels.

D.Kumaran, S.Eswaramoorthy, W.Furey, M.Sax, S.Swaminathan.

ABSTRACT

The three-dimensional structure of staphylococcal enterotoxin C2 (SEC2), a toxin as well as a superantigen, has been determined at various pH levels from two different crystal forms, tetragonal (pH 5.0, 5.5, 6.0 and 6.5) and monoclinic (pH 8.0) at 100 and 293 K, respectively, by the molecular-replacement method. Tetragonal crystals belong to space group P4(3)2(1)2, with unit-cell parameters a = b = 42.68, c = 289.15 A (at pH 5.0), and monoclinic crystals to space group P2(1), with unit-cell parameters a = 43.3, b = 70.6, c = 42.2 A, beta = 90.3 degrees. SEC2 contains a zinc-binding motif, D+HExxH, and accordingly a Zn atom has been identified. The coordination of the zinc ion suggests that it may be catalytic zinc rather than structural, but there is so far no biological evidence that it possesses catalytic activity. However, superantigen staphylococcal exfoliative toxins A and B have been shown to have enzymatic activity after their fold was identified to be similar to that of serine protease. The structure and its conformation are similar to the previously reported structures of SEC2. Though it was expected that the zinc ion may be leached out, as the histidines coordinating the zinc ion are expected to be protonated below pH 6.0, zinc is present at all pH values. The coordination distances to zinc increase with decreasing pH, with the distances being the least at pH 8.0. The results of automated model building using the ARP/wARP program for different data sets collected at various pH values are discussed.

Selected figure(s)

Figure 1.
Figure 1 Stereoviews of electron density corresponding to zinc in F[o] - F[c] and anomalous difference Fourier maps are shown in blue (5 ) and red (10 ) for the structure determined at pH 5.0. The refined zinc position is superposed on the residual density. Coordinating protein atoms are shown in ball-and-stick representation.

Figure 2.
Figure 2 A RIBBONS (Carson, 1991[Carson, M. (1991). J. Appl. Cryst. 24, 958-961.]) representation of SEC2. The zinc ion and coordination ligands are shown in ball-and-stick representation. -Helices and 3[10] helices are shown in red and blue, respectively.

The above figures are reprinted by permission from the IUCr: Acta Crystallogr D Biol Crystallogr (2001, 57, 1270-1275) copyright 2001.

Figures were selected by an automated process.