Crystal structures of two α-like scorpion toxins: Non-proline cis peptide bonds and implications for new binding site selectivity on the sodium channel

Xiao Lin He, Hong Min Li, Zong Hao Zeng, Xin Qi Liu, Miao Wang, Da Cheng Wang

Research output: Contribution to journalArticlepeer-review

79 Scopus citations


The crystal structures of two group III α-like toxins from the scorpion Buthus martensii Karsch, BmK M1 and BmK M4, were determined at 1.7 Å and 1.3 Å resolution and refined to R factors of 0.169 and 0.166, respectively. The first high-resolution structures of the α-like scorpion toxin show some striking features compared with structures of the 'classical' α-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 α-toxins. Sequence alignment and characteristics analysis suggested that the above structural features observed in BmK M1 and M4 occur in all group III α-like toxins. Recently, some group III α-like toxins were demonstrated to occupy a receptor site different from the classical α-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.

Original languageEnglish (US)
Pages (from-to)125-135
Number of pages11
JournalJournal of Molecular Biology
Issue number1
StatePublished - Sep 10 1999
Externally publishedYes


  • Binding selectivity
  • Buthus martensii Karsch
  • cis peptide bond
  • Crystal structure
  • Scorpion α-like toxin

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology


Dive into the research topics of 'Crystal structures of two α-like scorpion toxins: Non-proline cis peptide bonds and implications for new binding site selectivity on the sodium channel'. Together they form a unique fingerprint.

Cite this