A high-resolution solution structure of bucandin, a neurotoxin from Malayan krait (Bungarus candidus), was determined by 1H-NMR spectroscopy and molecular dynamics. The average backbone root-mean-square deviation for the 20 calculated structures and the mean structure is 0.47 Å (1 Å = 0.1nm) for all residues and 0.24 Å for the well-defined region that spans residues 23–58. Secondary-structural elements include two antiparallel β-sheets characterized by two and four strands. According to recent X-ray analysis, bucandin adopts a typical three-finger loop motif and yet it has some peculiar characteristics that set it apart from other common α-neurotoxins. The presence of a fourth strand in the second antiparallel β-sheet had not been observed before in three-finger toxins, and this feature was well represented in the NMR structure. Although the overall fold of the NMR structure is similar to that of the X-ray crystal structure, there are significant differences between the two structures that have implications for the pharmacological action of the toxin. These include the extent of the β-sheets, the conformation of the region spanning residues 42–49 and the orientation of some side chains. In comparison with the X-ray structure, the NMR structure shows that the hydrophobic side chains of Trp27 and Trp36 are stacked together and are orientated towards the tip of the middle loop. The NMR study also showed that the two-stranded β-sheet incorporated in the first loop, as defined by residues 1–22, and the C-terminus from Asn59, is probably flexible relative to the rest of the molecule. On the basis of the dispositions of the hydrophobic and hydrophilic side chains, the structure of bucandin is clearly different from those of cytotoxins.
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December 2001
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Research Article|
December 10 2001
NMR structure of bucandin, a neurotoxin from the venom of the Malayan krait (Bungarus candidus)
Allan M. TORRES;
Allan M. TORRES
∗Department of Biochemistry, University of Sydney, N. S. W. Australia 2006
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R. Manjunatha KINI;
R. Manjunatha KINI
†Department of Biological Sciences, Faculty of Science, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260
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Nirthanan SELVANAYAGAM;
Nirthanan SELVANAYAGAM
‡Department of Anatomy, Faculty of Medicine, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260
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Philip W. KUCHEL
Philip W. KUCHEL
1
∗Department of Biochemistry, University of Sydney, N. S. W. Australia 2006
1To whom correspondence should be addressed (e-mail p.kuchel@biochem.usyd.edu.au).
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Publisher: Portland Press Ltd
Received:
July 04 2001
Revision Received:
August 23 2001
Accepted:
October 08 2001
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London ©2001
2001
Biochem J (2001) 360 (3): 539–548.
Article history
Received:
July 04 2001
Revision Received:
August 23 2001
Accepted:
October 08 2001
Citation
Allan M. TORRES, R. Manjunatha KINI, Nirthanan SELVANAYAGAM, Philip W. KUCHEL; NMR structure of bucandin, a neurotoxin from the venom of the Malayan krait (Bungarus candidus). Biochem J 15 December 2001; 360 (3): 539–548. doi: https://doi.org/10.1042/bj3600539
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