1sn4
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(New page: 200px<br /><applet load="1sn4" size="450" color="white" frame="true" align="right" spinBox="true" caption="1sn4, resolution 1.3Å" /> '''STRUCTURE OF SCORPION...)
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Revision as of 00:23, 21 November 2007
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STRUCTURE OF SCORPION NEUROTOXIN BMK M4
Overview
The crystal structures of two group III alpha-like toxins from the, scorpion Buthus martensii Karsch, BmK M1 and BmK M4, were determined at, 1.7 A and 1.3 A resolution and refined to R factors of 0.169 and 0.166, respectively. The first high-resolution structures of the alpha-like, scorpion toxin show some striking features compared with structures of the, "classical" alpha-toxin. Firstly, a non-proline cis peptide bond between, residues 9 and 10 unusually occurs in the five-member reverse turn 8-12., Secondly, the cis peptide 9-10 mediates the spatial relationship between, the turn 8-12 and the C-terminal stretch 58-64 through a pair of, main-chain hydrogen bonds between residues 10 and 64 to form a unique, tertiary arrangement which features the special orientation of the, terminal residues 62-64. Finally, in consequence of the peculiar, orientation of the C-terminal residues, the functional groups of Arg58, which are crucial for the toxin-receptor interaction, are exposed and, accessible in BmK M1 and M4 rather than buried as in the classical, alpha-toxins. Sequence alignment and characteristics analysis suggested, that the above structural features observed in BmK M1 and M4 occur in all, group III alpha-like toxins. Recently, some group III alpha-like toxins, were demonstrated to occupy a receptor site different from the classical, alpha-toxin. Therefore, the distinct structural features of BmK M1 and M4, presented here may provide the structural basis for the newly recognized, toxin-receptor binding site selectivity. Besides, the non-proline cis, peptide bonds found in these two structures play a role in the formation, of the structural characteristics and in keeping accurate positions of the, functionally crucial residues. This manifested a way to achieve high, levels of molecular specificity and atomic precision through the strained, backbone geometry.
About this Structure
1SN4 is a Single protein structure of sequence from Mesobuthus martensii with ACT as ligand. Full crystallographic information is available from OCA.
Reference
Crystal structures of two alpha-like scorpion toxins: non-proline cis peptide bonds and implications for new binding site selectivity on the sodium channel., He XL, Li HM, Zeng ZH, Liu XQ, Wang M, Wang DC, J Mol Biol. 1999 Sep 10;292(1):125-35. PMID:10493862
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