Cyclic α-
conotoxin Vc1.1 (cVc1.1) is an orally active
peptide with
analgesic activity in rat models of
neuropathic pain. It has two
disulfide bonds, which can have three different connectivities, one of which is the native and active form. In this study we used computational modeling and nuclear magnetic resonance to design a
disulfide-deleted mutant of cVc1.1, [C2H,C8F]cVc1.1, which has a larger hydrophobic core than cVc1.1 and, potentially, additional surface
salt bridge interactions. The new variant, hcVc1.1, has similar structure and serum stability to cVc1.1 and is highly stable at a wide range of pH and temperatures. Remarkably, hcVc1.1 also has similar selectivity to cVc1.1, as it inhibited recombinant human α9α10
nicotinic acetylcholine receptor-mediated currents with an IC50 of 13 μM and rat N-type (Cav2.2) and recombinant human Cav2.3
calcium channels via GABAB receptor activation, with an IC50 of ~900 pM. Compared to cVc1.1, the potency of hcVc1.1 is reduced three-fold at both
analgesic targets, whereas previous attempts to replace Vc1.1
disulfide bonds by non-reducible dicarba linkages resulted in at least 30-fold decreased activity. Because it has only one
disulfide bond, hcVc1.1 is not subject to
disulfide bond shuffling and does not form multiple isomers during
peptide synthesis.