PDBsum entry 1zu3

Toxin

PDB id: 1zu3

Contents

Protein chain

64 a.a. *

Waters ×57

* Residue conservation analysis

PDB id:

1zu3

Name:

Toxin

Title:

Crystal structure of mutant k8a of scorpion alpha-like neurotoxin bmk m1 from buthus martensii karsch

Structure:

Alpha-like neurotoxin bmk-i. Chain: a. Synonym: bmk i, bmki, bmk1, bmk-m1, bmk m1, bmkm1. Engineered: yes. Mutation: yes

Source:

Mesobuthus martensii. Chinese scorpion. Organism_taxid: 34649. Gene: bmk m1. Expressed in: saccharomyces cerevisiae. Expression_system_taxid: 4932.

Resolution:

1.33Å R-factor: 0.172 R-free: 0.190

Authors:

X.Ye,F.Bosmans,C.Li,Y.Zhang,D.C.Wang,J.Tytgat

Key ref:

X.Ye et al. (2005). Structural basis for the voltage-gated Na+ channel selectivity of the scorpion alpha-like toxin BmK M1. J Mol Biol, 353, 788-803. PubMed id: 16209876 DOI: 10.1016/j.jmb.2005.08.068

Date:

30-May-05 Release date: 23-May-06

Protein chain

P45697  (SCM1_MESMA) -  Alpha-like toxin BmK M1 from Mesobuthus martensii

Seq: 84 a.a.

Struc: 64 a.a.*

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

DOI no: 10.1016/j.jmb.2005.08.068

J Mol Biol 353:788-803 (2005)

PubMed id: 16209876

Structural basis for the voltage-gated Na+ channel selectivity of the scorpion alpha-like toxin BmK M1.

X.Ye, F.Bosmans, C.Li, Y.Zhang, D.C.Wang, J.Tytgat.

ABSTRACT

Scorpion alpha-like toxins are proteins that act on mammalian and insect voltage-gated Na+ channels. Therefore, these toxins constitute an excellent target for examining the foundations that underlie their target specificity. With this motive we dissected the role of six critical amino acids located in the five-residue reverse turn (RT) and C-tail (CT) of the scorpion alpha-like toxin BmK M1. These residues were individually substituted resulting in 11 mutants and were subjected to a bioassay on mice, an electrophysiological characterization on three cloned voltage-gated Na+ channels (Nav1.2, Nav1.5 and para), a CD analysis and X-ray crystallography. The results reveal two molecular sites, a couplet of residues (8-9) in the RT and a hydrophobic surface consisting of residues 57 and 59-61 in the CT, where the substitution with specific residues can redirect the alpha-like characteristics of BmK M1 to either total insect or much higher mammal specificity. Crystal structures reveal that the pharmacological ramification of these mutants is accompanied by the reshaping of the 3D structure surrounding position 8. Furthermore, our results also reveal that residues 57 and 59-61, located at the CT, enclose the critical residue 58 in order to form a hydrophobic "gasket". Mutants of BmK M1 that interrupt this hydrophobic surface significantly gain insect selectivity.

Selected figure(s)

Figure 4.
Figure 4. (a) Electron density maps around the mutated residues at position 8 (up) (omit F[o] -F[c] maps, contoured at 3.0s) and the reverse turn (8-12) in different conformational states with trans peptide bond 9-10 (K8D) and cis peptide bond 9-10 (K8Q, K8A and K8G) (down) (2F[o] -F[c] maps contoured at 1.0s). (b) Main-chain trace superimposition of eight mutant structures.

Figure 5.
Figure 5. (a) Conformational state surrounding residue 8 in different mutants and native BmK M1. Residues around position 8 including 8-12 and 63-64 are space-filled and coloured according to their chemical nature and locations (carbon atoms of residues 8-11 and residue 64 are green and cyan, respectively; nitrogen and oxygen atoms of these residues are in blue and red, respectively; two cysteine residues 12 and 63 are yellow). Broken lines with different colours highlight the surface of residue 8 (positive, blue; negative, red; neutral, green). (b) Distinct structures of the five-residue reverse turn (RT) in association with the C-tail (CT) of the mutants containing trans peptide bond 9-10 (K8D and K8D/P9S) and cis peptide bond 9-10 (K8Q, K8A and K8G). In the trans-containing form, the peptide group NH10 is situated inside the turn and residue 8 must be Asp, which interact with each other via hydrogen bond N10...Od1 8. There is no contact between the NH10 group and the C-terminal residue, referred to as transRT-freeCT. In cis-containing form group NH10 points out of the reverse turn and interacts with the C-terminal residue via hydrogen bond N10...O64, referred to as cisRT-bondCT. The side-chain of H10 is not shown.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2005, 353, 788-803) copyright 2005.

Figures were selected by an automated process.