1s8k

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Solution Structure of BmKK4, A Novel Potassium Channel Blocker from Scorpion Buthus martensii Karsch, 25 structures

Overview

BmKK4 is a 30 amino acid peptide purified from the venom of the Chinese, scorpion Buthus martensi Karsch. It has been classified as the first, member of scorpion toxin subfamily alpha-KTx 17. The 3D structure of BmKK4, in solution has been determined by 2D NMR spectroscopy. This toxin adopts, a common alpha/beta-motif, but shows a distinctive local conformation. The, most novel feature is that the regular arrangements of the side chains of, the residues involved in the beta-sheet of BmKK4 are distorted by a, classic beta-bulge structure, which involves two residues (Asp18 and, Arg19) in the first strand opposite a single residue (Tyr26) in the second, strand. The bulge produces two main changes in the structure of the, antiparallel beta-sheet: (1) It disrupts the normal alteration of the side, chain direction; the side chain of Asp18 turns over to form a salt bridge, with that of Arg19. (2) It accentuates the twist of the sheet, and alters, the direction of the antiparallel beta-sheet. The unusual structural, feature of the toxin is attributed to the shorter peptide segment, (Leu15-Arg19) between the third and fourth Cys residues and two unique, residues (Asp18 and Arg19) at the position preceding the fourth Cys. In, addition, the lower affinity of the peptide for the Kv channel is, correlated to the structural features: residue Arg19 instead of a Lys, residue at the critical position for binding and the salt bridge formed, between residues Arg19 and Asp18.

About this Structure

1S8K is a Single protein structure of sequence from Mesobuthus martensii with NH2 as ligand. Full crystallographic information is available from OCA.

Reference

Solution structure of BmKK4, the first member of subfamily alpha-KTx 17 of scorpion toxins., Zhang N, Chen X, Li M, Cao C, Wang Y, Wu G, Hu G, Wu H, Biochemistry. 2004 Oct 5;43(39):12469-76. PMID:15449936

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