PDBsum entry 1wwn

Toxin

PDB id: 1wwn

Contents

Protein chain

69 a.a.

References listed in PDB file

Key reference

• Title: Nmr solution structure of bmk-Betait, An excitatory scorpion beta-Toxin without a 'Hot spot' At the relevant position.
• Authors: X.Tong, J.Yao, F.He, X.Chen, X.Zheng, C.Xie, G.Wu, N.Zhang, J.Ding, H.Wu.
• Ref.: Biochem Biophys Res Commun, 2006, 349, 890-899. [DOI no: 10.1016/j.bbrc.2006.08.131]
• PubMed id: 16970911

Abstract

BmK-betaIT (previously named as Bm32-VI in the literature), an excitatory scorpion beta-toxin, is purified from the venom of the Chinese scorpion Buthus martensii Karsch. It features a primary sequence typical of the excitatory anti-insect toxins: two contiguous Cys residues (Cys37-Cys38) and a shifted location of the fourth disulfide bridges (Cys38-Cys64), and demonstrates bioactivity characteristic of the excitatory beta-toxins. However, it is noteworthy that BmK-betaIT is not conserved with a glutamate residue at the preceding position of the third Cys residue, and is the first example having a non-glutamate residue at the relevant position in the excitatory scorpion beta-toxin subfamily. The 3D structure of BmK-betaIT is determined with 2D NMR spectroscopy and molecular modeling. The solution structure of BmK-betaIT is closely similar to those of BmK IT-AP and Bj-xtrIT, only distinct from the latter by lack of an alpha(0)-helix. The surface functional patch comparison with those of BmK IT-AP and Bj-xtrIT reveals their striking similarity in the spatial arrangement. These results infer that the functional surface of beta-toxins is composed of two binding regions and a functional site. The main binding site is consisted of hydrophobic residues surrounding the alpha(1)-helix and its preceding loop, which is common to all beta-type scorpion toxins affecting Na(+) channels. The second binding site, which determines the specificity of the toxin, locates at the C-terminus for excitatory insect beta-toxin, while rests at the beta-sheet and its linking loop for anti-mammal toxins. The functional site involved in the voltage sensor-trapping model, which characterizes the function of all beta-toxins, is the negatively charged residue Glu15.