1WWN

NMR Solution Structure of BmK-betaIT, an Excitatory Scorpion Toxin from Buthus martensi Karsch

Summary for 1WWN

• Entry DOI: 10.2210/pdb1wwn/pdb
• Related: 1BCG 1NPI 1PTX
• Descriptor: Excitatory insect selective toxin 1 (1 entity in total)
• Functional Keywords: an excitatory scorpion toxin, toxin
• Biological source: Mesobuthus martensii (Chinese scorpion)
• Cellular location: Secreted: O61668
• Total number of polymer chains: 1
• Total formula weight: 7649.80

Authors

Wu, H.,Tong, X.,Chen, X.,Zhang, Q.,Zheng, X.,Zhang, N.,Wu, G. (deposition date: 2005-01-10, release date: 2006-01-17, Last modification date: 2024-10-23)

Primary citation

Tong, X.,Yao, J.,He, F.,Chen, X.,Zheng, X.,Xie, C.,Wu, G.,Zhang, N.,Ding, J.,Wu, H.
NMR solution structure of BmK-betaIT, an excitatory scorpion beta-toxin without a 'hot spot' at the relevant position
Biochem.Biophys.Res.Commun., 349:890-899, 2006

PubMed 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.

PubMed: 16970911
DOI: 10.1016/j.bbrc.2006.08.131

Experimental method

SOLUTION NMR