PDBsum entry 1bcg

Excitatory neurotoxin

PDB id: 1bcg

Contents

Protein chain

74 a.a. *

Waters ×72

* Residue conservation analysis

PDB id:

1bcg

Name:

Excitatory neurotoxin

Title:

Scorpion toxin bjxtr-it

Structure:

Toxin bjxtr-it. Chain: a

Source:

Hottentotta judaicus. Organism_taxid: 6863

Biol. unit:

Dimer (from PQS)

Resolution:

2.10Å R-factor: 0.209 R-free: 0.256

Authors:

D.Oren,O.Froy,E.Amit,N.Kleinberger-Doron,M.Gurevitz,B.Shaanan

Key ref:

D.A.Oren et al. (1998). An excitatory scorpion toxin with a distinctive feature: an additional alpha helix at the C terminus and its implications for interaction with insect sodium channels. Structure, 6, 1095-1103. PubMed id: 9753689 DOI: 10.1016/S0969-2126(98)00111-7

Date:

29-Apr-98 Release date: 18-Nov-98

Protein chain

P56637  (SIXE_HOTJU) -  Beta-insect excitatory toxin Bj-xtrIT from Hottentotta judaicus

Seq: 94 a.a.

Struc: 74 a.a.*

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

DOI no: 10.1016/S0969-2126(98)00111-7

Structure 6:1095-1103 (1998)

PubMed id: 9753689

An excitatory scorpion toxin with a distinctive feature: an additional alpha helix at the C terminus and its implications for interaction with insect sodium channels.

D.A.Oren, O.Froy, E.Amit, N.Kleinberger-Doron, M.Gurevitz, B.Shaanan.

ABSTRACT

BACKGROUND: Scorpion neurotoxins, which bind and modulate sodium channels, have been divided into two groups, the alpha and beta toxins, according to their activities. The beta-toxin class includes the groups of excitatory and depressant toxins, which differ in their mode of action and are highly specific against insects. The three-dimensional structures of several alpha and beta toxins have been determined at high resolution, but no detailed 3D structure of an excitatory toxin has been presented so far. RESULTS: The crystal structure of an anti-insect excitatory toxin from the scorpion Buthotus judaicus, Bj-xtrIT, has been determined at 2.1 A resolution and refined to an R factor of 0.209. The first 59 residues form a closely packed module, structurally similar to the conserved alpha and beta toxins ('long toxins') affecting sodium channels. The last 17 residues form a C-terminal extension not previously seen in scorpion toxins. It comprises a short alpha helix anchored to the N-terminal module by a disulfide bridge and is followed by a highly mobile stretch of seven residues, of which only four are seen in the electron-density map. This mobile peptide covers part of a conserved hydrophobic surface that is thought to be essential for interaction with the channel in several long toxins. CONCLUSIONS: Replacement of the last seven residues by a single glycine abolishes the activity of Bj-xtrIT, strongly suggesting that these residues are intimately involved in the interaction with the channel. Taken together with the partial shielding of the conserved hydrophobic surface and the proximity of the C terminus to an adjacent surface rich in charged residues, it seems likely that the bioactive surface of Bj-xtrIT is formed by residues surrounding the C terminus. The 3D structure and a recently developed expression system for Bj-xtrIT pave the way for identifying the structural determinants involved in the bioactivity and anti-insect specificity of excitatory toxins.

Selected figure(s)

Figure 4.
Figure 4. Overall structures of (a) CsE-v3, (b) Bj-xtrIT and (c) AaHII, viewed in the same orientation. Structural elements of Bj-xtrIT are in the same color scheme as in Figure 2. On each panel, the disulfide bridges are numbered 1-3 for conserved and, 4 for nonconserved (see text and Figure 2). The figure was prepared using the program MOLSCRIPT [45].

The above figure is reprinted by permission from Cell Press: Structure (1998, 6, 1095-1103) copyright 1998.

Figure was selected by an automated process.