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Acta Biochimica et Biophysica Sinica Advance Access originally published online on September 3, 2009
Acta Biochimica et Biophysica Sinica 2009 41(10):858-864; doi:10.1093/abbs/gmp077
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© The Author 2009. Published by ABBS Editorial Office in association with Oxford University Press on behalf of the Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences.

Characterization of a novel {alpha}4/4-conotoxin, Qc1.2, from vermivorous Conus quercinus

Can Peng1, Weihua Chen1, Yuhong Han2, Tanya Sanders3, Geoffrey Chew3, Jing Liu3, Edward Hawrot3, Chengwu Chi1,2,* and Chunguang Wang1,*

1 Institute of Protein Research, Tongji University, Shanghai 200092, China
2 Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
3 Department of Molecular Pharmacology, Physiology and Biotechnology, Brown Medical School, Providence, RI 02912, USA

* Correspondence address. Tel: +86-21-65984347; Fax: +86-21-65988403; E-mail: chunguangwang{at}tongji.edu.cn (C.W.); Tel: +86-21-54921165; Fax: +86 21-54921011; E-mail: zwqi{at}sibs.ac.cn (C.C.)


  Abstract

As part of continuing studies of the identification of gene organization and cloning of novel {alpha}-conotoxins, the first {alpha}4/4-conotoxin identified in a vermivorous Conus species, designated Qc1.2, was originally obtained by cDNA and genomic DNA cloning from Conus quercinus collected in the South China Sea. The predicted mature toxin of Qc1.2 contains 14 amino acid residues with two disulfide bonds (I-III, II-IV connectivity) in a native globular configuration. The mature peptide of Qc1.2 is supposed to contain an N-terminal post-translationally processed pyroglutamate residue and a free carboxyl C-terminus. This peptide was chemically synthesized and refolded for further characterization of its functional properties. The synthetic Qc1.2 has two interconvertible conformations in aqueous solution, which may be due to the cis-trans isomerization of the two successive Pro residues in its first Cys loop. Using the Xenopus oocyte heterologous expression system, Qc1.2 was shown to selectively inhibit both rat neuronal {alpha}3β2 and {alpha}3β4 subtypes of nicotinic acetylcholine receptors with low potency. A block of ~63% and 37% of the ACh-evoked currents was observed, respectively, and the toxin dissociated rapidly from the receptors. Compared with other characterized {alpha}-conotoxin members, the unusual structural features in Qc1.2 that confer to its receptor recognition profile are addressed.

Keywords    nicotinic acetylcholine receptor subtype; {alpha}4/4-conotoxin; post-translational modification; Xenopus oocyte

Received: May 16, 2009; Accepted: June 26, 2009
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