Structure-Activity Analysis of a Conus Peptide Blocker of N-Type Neuronal Calcium Channels

Abstract

The synthetic peptide SNX-111 corresponding to the sequence of the omega-conopeptide MVIIA from the venom of the marine snail Conus magus is a highly potent and selective antagonist of N-type calcium channels. We have synthesized and characterized a large number of analogs of SNX-111 in order to elucidate the structural features of the peptide involved in blocking N-type calcium channels. Comparison of the binding of SNX-111 and its analogs to rat brain synaptosomal membranes rich in N-type channels revealed that, among the four lysines and two arginines in the molecule, lysine in position 2 and arginines at position 10 and 21 are important for the interaction of SNX-111 with N-type channels. The importance of the middle segment from residues 9 through 14 for this binding interaction was revealed by substitution of the individual residues as well as by the construction of hybrid peptides in which the residues 9-12 in SNX-111 and another conopeptide, SNX-183, corresponding to a peptide SVIB from Conus striatus, were interchanged. Introduction of the sequence SRLM from SNX-111 in place of RKTS in position 9-12 in SNX-183 resulted in a 38-fold increase in affinity.

Solution structure of ω‐conotoxin MVIIA using 2D NMR spectroscopy

“…That leaves the region of Y13-D14 or the region of K2-G3, as recently also suggested by systematic alanine substitutions in og-CmTxa [45]. In both of these regions the • and ~ angles in og-CmTxc are significantly different from co-CmTxa and o9-CgTx, while the latter two have the same backbone angles.…”

“…In both of these regions the • and ~ angles in og-CmTxc are significantly different from co-CmTxa and o9-CgTx, while the latter two have the same backbone angles. Mutation of Y13 to F reduces the binding of og-CgTx by 3 orders of magnitude [46], and of og-CmTxa by 2.5 orders [45], which means that this tyrosine is essential for binding. Iodination of Y13 only slightly alters the binding affinities and selectivities of og-CmTxa and og-CmTxc, suggesting that the phenolic OH group is important here.…”

“…These studies were, however, limited to lysine modifications only. Synthetic analogues of co-CmTxa have been made replacing each positively charged residue with an alanine, one at a time, and it was found that positions 2, 10 and 21 are important for binding, while Ala at position 24 shows no effect [45]. Some of the ambiguities with these results can be understood by the fact that most of the positively charged residues have a lot of flexibility since the charges are at the end of their long flexible sidechains, so that one missing charge could be replaced with the sidechain of another positively charged sidechain.…”

ConusVenoms: A Rich Source of Novel Ion Channel-Targeted Peptides

“…The structure of several -conotoxins has been solved. A characteristic feature of -conotoxins is their high content of basic amino acid residues that are known to play an important role for the inhibition of Ca channels (132). Besides these positive charges, it is known that a tyrosine residue (Tyr-13 in -MVIIA and -MVIIC) is important for the binding to Ca v 2.2 and Ca v 2.1 channels (90,102,134).…”

Conotoxins: from the biodiversity of gastropods to new drugs

“…Структурные исследования показали, что в первичной структуре w-конотоксинов высоко содержание основных аминокислотных остатков, которые, как известно, играют важную роль в ингибировании Са-каналов [100].…”