Mammalian neuronal sodium channel Blocker mu-conotoxin BuIIIB has a structured N-terminus that influences potency

Kuang, Zhihe and Zhang, Min-Min and Gupta, Kallol and Gajewiak, Joanna and Gulyas, Jozsef and Balaram, Padmanabhan and Rivier, Jean E and Olivera, Baldomero M and Yoshikami, Doju and Bulaj, Grzegorz and Norton, Raymond S (2013) Mammalian neuronal sodium channel Blocker mu-conotoxin BuIIIB has a structured N-terminus that influences potency. In: ACS Chemical Biology, 8 (6). pp. 1344-1351.

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Abstract

Among the mu-conotoxins that block vertebrate voltage-gated sodium channels (VGSCs), some have been shown to be potent analgesics following systemic administration in mice. We have determined the solution structure of a new representative of this family, mu-BuIIIB, and established its disulfide connectivities by direct mass spectrometric collision induced dissociation fragmentation of the peptide with disulfides intact The major oxidative folding product adopts a 1-4/2-5/3-6 pattern with the following disulfide bridges: Cys5-Cys17, Cys6-Cys23, and Cys13-Cys24. The solution structure reveals that the unique N-terminal extension in mu-BuIIIB, which is also present in mu-BuIIIA and mu-BuIIIC but absent in other mu-conotoxins, forms part of a short a-helix encompassing Glu3 to Asn8. This helix is packed against the rest of the toxin and stabilized by the Cys5-Cys17 and Cys6-Cys23 disulfide bonds. As such, the side chain of Val1 is located close to the aromatic rings of Trp16 and His20, which are located on the canonical helix that displays several residues found to be essential for VGSC blockade in related mu-conotoxins. Mutations of residues 2 and 3 in the N-terminal extension enhanced the potency of mu-BuIIIB for Na(v)1.3. One analogue, D-Ala2]BuIIIB, showed a 40-fold increase, making it the most potent peptide blocker of this channel characterized to date and thus a useful new tool with which to characterize this channel. On the basis of previous results for related mu-conotoxins, the dramatic effects of mutations at the N-terminus were unanticipated and suggest that further gains in potency might be achieved by additional modifications of this region.

Item Type:	Journal Article
Publication:	ACS Chemical Biology
Publisher:	American Chemical Society
Additional Information:	Copyright of this article belongs to American Chemical Society.
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited:	20 Sep 2013 12:12
Last Modified:	20 Sep 2013 12:12
URI:	http://eprints.iisc.ac.in/id/eprint/47224

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