Solution Structure of BmKIT01, an -Insect Toxin from the Venom of the Chinese Scorpion Buthus martensii Karsch
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- 作者：Xiaotian Tong ; Jing Zhu ; Yuguang Ma ; Xiang Chen ; Gong Wu ; Fahu He ; Chunyang Cao ; Houming Wu
- 刊名：Biochemistry
- 出版年：2007
- 出版时间：October 9, 2007
- 年：2007
- 卷：46
- 期：40
- 页码：11322 - 11330
- 全文大小：448K
- 年卷期：v.46,no.40(October 9, 2007)
- ISSN：1520-4995
文摘
The solution structure of an -insect toxin from Buthus martensii Karsch, BmKIT01, hasbeen determined by two-dimensional NMR spectroscopy and molecular modeling techniques. Combiningthe sequence homology comparison and toxicity bioassays, BmKIT01 has been suggested to be a naturalmutant of -insect toxins and so can serve as a tool to study the relationship of structure-function amongthis group of toxins. The overall structure of BmKIT01 shares a common core structure consisting of an-helix packed against a three-stranded antiparallel -sheet, which exhibits distinctive local conformationswithin the loops connecting these secondary structure elements. The solution structure of BmKIT01features a non-proline cis peptide bond between Asn9 and Tyr10, which is proposed to mediate the spatialclosing of the five-residue turn (Gln8-Cys12) and the C-terminal segment (Arg58-His64) to form theNC domain and confer the toxin insect-specific bioactivity. Conformational heterogeneity is observed inthe solution of BmKIT01 and could be attributed to the cis-trans isomerization of the peptide bondbetween residues 9 and 10. The minor conformation of BmKIT01 with a trans peptide bond betweenAsn9 and Tyr10 may be responsible for its moderate bioactivity against mammals. The cis-transisomerization of the peptide bond between residues 9 and 10 may be the structural basis of dualpharmacological activities of -insect and -like scorpion toxins, which is supported by the fact thatconformational heterogeneity occurs in the solution structures of LqhIT, LqqIII, and LqhIII and bycomparison of the solution structure of BmKIT01 with those of some relevant -type toxins.