Nmr Solution Structure of Bmk-betait, an Excitatory Scorpion Beta-toxin Without a 'hot Spot' at the Relevant Position.
From: State Key Laboratory of Bio-organic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China.
Biochemical and biophysical research communications
- Publish Date: Oct 2006
- ISSN: 0006-291X
- Volume: 349
- Issue: 3
- Pages: 890-9
- Medium: Print
- Language: English
- Citation (JAMA): Tong Xiaotian, Yao Jing, He Fahu, et al. Nmr Solution Structure of Bmk-betait, an Excitatory Scorpion Beta-toxin Without a 'hot Spot' at the Relevant Position.. Biochem. Biophys. Res. Commun. Oct 2006;349:890-9
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.
Mesh Headings (Keywords): Amino Acid Sequence, Amino Acids, Animals, Models, Molecular, Molecular Sequence Data, Nuclear Magnetic Resonance, Biomolecular, Protein Structure, Secondary, Protein Structure, Tertiary, Scorpion Venoms, Scorpions, Sequence Alignment
Check for Full Text / PubMed Unique Identifier (PMID): 16970911
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