PDBsum entry 1kd6

Membrane protein

PDB id: 1kd6

Contents

Protein chain

179 a.a. *

* Residue conservation analysis

PDB id:

1kd6

Name:

Membrane protein

Title:

Solution structure of the eukaryotic pore-forming cytolysin equinatoxin ii

Structure:

Equinatoxin ii. Chain: a. Synonym: eqtii, tenebrosin c. Engineered: yes

Source:

Actinia equina. Organism_taxid: 6106. Expressed in: escherichia coli bl21(de3). Expression_system_taxid: 469008.

NMR struc:

20 models

Authors:

M.G.Hinds,W.Zhang,G.Anderluh,P.E.Hansen,R.S.Norton

Key ref:

M.G.Hinds et al. (2002). Solution structure of the eukaryotic pore-forming cytolysin equinatoxin II: implications for pore formation. J Mol Biol, 315, 1219-1229. PubMed id: 11827489 DOI: 10.1006/jmbi.2001.5321

Date:

12-Nov-01 Release date: 13-Feb-02

Protein chain

P61914  (ACTP2_ACTEQ) -  DELTA-actitoxin-Aeq1a from Actinia equina

Seq: 214 a.a.

Struc: 179 a.a.*

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

Enzyme reactions

• Enzyme class: E.C.?

DOI no: 10.1006/jmbi.2001.5321

J Mol Biol 315:1219-1229 (2002)

PubMed id: 11827489

Solution structure of the eukaryotic pore-forming cytolysin equinatoxin II: implications for pore formation.

M.G.Hinds, W.Zhang, G.Anderluh, P.E.Hansen, R.S.Norton.

ABSTRACT

Sea anemones produce a family of 18-20 kDa proteins, the actinoporins, that lyse cells by forming pores in cell membranes. Sphingomyelin plays an important role in their lytic activity, with membranes lacking this lipid being largely refractory to these toxins. The structure of the actinoporin equinatoxin II in aqueous solution, determined from NMR data, consists of two short helices packed against opposite faces of a beta-sandwich structure formed by two five-stranded beta-sheets. The protein core has extensive hydrophobic interfaces formed by residues projecting from the internal faces of the two beta-sheets. 15N relaxation data show uniform backbone dynamics, implying that equinatoxin II in solution is relatively rigid, except at the N terminus; its inferred rotational correlation time is consistent with values for monomeric proteins of similar mass. Backbone amide exchange rate data also support the view of a stable structure, even though equinatoxin II lacks disulfide bonds. As monitored by NMR, it unfolds at around 70 degrees C at pH 5.5. At 25 degrees C the structure is stable over the pH range 2.5-7.3 but below pH 2.5 it undergoes a slow transition to an incompletely unfolded structure resembling a molten globule. Equinatoxin II has two significant patches of positive electrostatic potential formed by surface-exposed Lys and Arg residues, which may assist its interaction with charged regions of the lipid head groups. Tyr and Trp residues on the surface may also contribute by interacting with the carbonyl groups of the acyl chains of target membranes. Data from mutational studies and truncated analogues identify two regions of the protein involved in membrane interactions, the N-terminal helix and the Trp-rich region. Once the protein is anchored, the N-terminal helix may penetrate the membrane, with up to four helices lining the pore, although other mechanisms of pore formation cannot be ruled out.

Selected figure(s)

Figure 1.
Figure 1. Stereo view of family of 20 structures of EqTII superimposed over the backbone heavy atoms (N, C^a, C) of the b-strands (b1 residues 32-40, b2 46-53, b3 69-75, b4 86-94, b5 98-106, b6 115-124, b7 143-145, b8 150-154, b9 158-165 and b10 170-177).

Figure 2.
Figure 2. (a) Ribbon diagram generated using MOLMOL[62] of structure closest to the mean showing elements of secondary structure with the Trp residues depicted in orange and the Tyr residues in blue. The right-hand view is related to the left by a 90° rotation about the vertical axis and a slight tilt towards the viewer. (b) Surface charge potential distribution on EqTII showing two views related by a 180° rotation about the vertical axis. The right-hand image depicts a similar view to the left-hand image of (a). Areas of negative potential are coloured red and positive potential blue. This Figure was created using the program GRASP. [63] The potential is displayed over the range < -8k[b]T and >+8k[b]T, where k[b] is the Boltzmann constant and T the temperature.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2002, 315, 1219-1229) copyright 2002.

Figures were selected by an automated process.