1sxm
From Proteopedia
SCORPION TOXIN (NOXIUSTOXIN) WITH HIGH AFFINITY FOR VOLTAGE DEPENDENT POTASSIUM CHANNEL AND LOW AFFINITY FOR CALCIUM DEPENDENT POTASSIUM CHANNEL (NMR AT 20 DEGREES, PH3.5, 39 STRUCTURES)
Overview
The 3D structure of noxiustoxin, the first identified scorpion toxin acting on K+ channels, has been elucidated by NMR and molecular modeling. Thirty-nine solution structures were calculated using 572 distance and 42 dihedral restraints. The average atomic rms deviation between the refined structures and the mean structure is 0.75 A for the backbone atoms. Noxiustoxin adopts a alpha/beta scaffold constituted of a three-stranded beta-sheet (residues 2-3, 25-30, 33-38) linked to a helix (residues 10-20) through two disulfide bridges. A comparison between the 3D structure of noxiustoxin and those of other structurally and functionally related scorpion toxins (charybdotoxin, PO5-NH2, kaliotoxin) revealed a bending capacity of the helix and a variability in the relative orientations between the helix and the beta-sheet. These two features highlight the plasticity of the alpha/beta scaffold and offer a structural explanation for the capacity of the fold to accommodate an additional alanine residue in the Gly-x-Cys pattern of a previously proposed consensus sequence [Bontems et al. (1991) Science 254, 1521-1523]. Our structural data also emphasize the possibility that the beta-sheet of NTX is implicated in the capacity of NTX to recognize voltage-dependent K+ channels.
About this Structure
1SXM is a Single protein structure of sequence from Centruroides noxius. Full crystallographic information is available from OCA.
Reference
Determination of the three-dimensional solution structure of noxiustoxin: analysis of structural differences with related short-chain scorpion toxins., Dauplais M, Gilquin B, Possani LD, Gurrola-Briones G, Roumestand C, Menez A, Biochemistry. 1995 Dec 26;34(51):16563-73. PMID:8527429 Page seeded by OCA on Sat May 3 09:15:22 2008
