Search

Ziconotide (ω‐conotoxin MVIIA) is an approved analgesic for the treatment of chronic pain. However, the need for intrathecal administration and adverse effects have limited its widespread application. Backbone cyclization is one way to improve the pharmaceutical properties of conopeptides, but so far chemical synthesis alone has been unable to produce correctly folded and backbone cyclic analogues of MVIIA. In this study, an asparaginyl endopeptidase (AEP)‐mediated cyclization was used to generate backbone cyclic analogues of MVIIA for the first time. Cyclization using six‐ to nine‐residue linkers did not perturb the overall structure of MVIIA, and the cyclic analogues of MVIIA showed inhibition of voltage‐gated calcium channels (CaV2.2) and substantially improved stability in human serum and stimulated intestinal fluid. Our study reveals that AEP transpeptidases are capable of cyclizing structurally complex peptides that chemical synthesis cannot achieve and paves the way for further improving the therapeutic value of conotoxins. [ABSTRACT FROM AUTHOR]

Macrocyclic, disulfide-rich peptides have found widespread applications in drug design and development. Current peptide production strategies rely heavily on solid phase peptide synthesis (SPPS) requiring large amounts of hazardous/toxic reagents and solvents which have negative environmental impacts. A possible solution is to develop a sustainable hybrid production platform incorporating recombinant production of cyclic peptide precursors in yeast followed by enzymatic maturation of these precursors into cyclic peptides using asparaginyl endopeptidases in vitro. Harnessing the efficient secretory pathway of Pichia pastoris, peptide precursors, cloned downstream of the α-mating factor secretion signal, were purified from culture supernatant mitigating the need for complex purification. To demonstrate the broad utility of the platform, three distinct classes of cyclic peptides were produced; two were structurally validated by NMR and shown to be functionally equivalent to their synthetically produced versions. Furthermore, using this platform we report the first recombinant production of any α-conotoxin in its native "globular" conformation. Using scale-up production in bioreactors, cyclic peptide yields of 85–97 mg L−1 of culture were achieved, far exceeding the highest yields so far achieved for cyclic disulfide-rich peptides in any recombinant process. This platform can potentially unlock production and facilitate applications of cyclic disulfide-rich peptides previously inaccessible through large-scale chemical synthesis and reduce their environmental burden. [ABSTRACT FROM AUTHOR]

Mambalgins are a novel class of snake venom components that exert potent analgesic effects mediated through the inhibition of acid-sensing ion channels (ASICs). The 57-residue polypeptide mambalgin-2 (Ma-2) was synthesized by using a combination of solid-phase peptide synthesis and native chemical ligation. The structure of the synthetic toxin, determined using homonuclear NMR, revealed an unusual three-finger toxin fold reminiscent of functionally unrelated snake toxins. Electrophysiological analysis of Ma-2 on wild-type and mutant ASIC1a receptors allowed us to identify α-helix 5, which borders on the functionally critical acidic pocket of the channel, as a major part of the Ma-2 binding site. This region is also crucial for the interaction of ASIC1a with the spider toxin PcTx1, thus suggesting that the binding sites for these toxins substantially overlap. This work lays the foundation for structure-activity relationship (SAR) studies and further development of this promising analgesic peptide. [ABSTRACT FROM AUTHOR]

We report the total chemical synthesis of human C3a by one-pot native chemical ligation of three unprotected peptide segments, followed by efficient in vitro folding that yielded the anaphylatoxin C3a in high yield and excellent purity. Synthetic C3a was fully active and its crystal structure at 2.1 Å resolution showed 3 helices and a C-terminal turn motif. [ABSTRACT FROM AUTHOR]

Abstract: Spider venoms are replete with peptidic ion channel modulators, often with novel subtype selectivity, making them a rich source of pharmacological tools and drug leads. In a search for subtype-selective blockers of voltage-gated calcium (CaV) channels, we isolated and characterized a novel 39-residue peptide, ω-TRTX-Cc1a (Cc1a), from the venom of the tarantula Citharischius crawshayi (now Pelinobius muticus). Cc1a is 67% identical to the spider toxin ω-TRTX-Hg1a, an inhibitor of CaV2.3 channels. We assembled Cc1a using a combination of Boc solid-phase peptide synthesis and native chemical ligation. Oxidative folding yielded two stable, slowly interconverting isomers. Cc1a preferentially inhibited Ba2+ currents (I Ba) mediated by L-type (CaV1.2 and CaV1.3) CaV channels heterologously expressed in Xenopus oocytes, with half-maximal inhibitory concentration (IC50) values of 825nM and 2.24μM, respectively. In rat dorsal root ganglion neurons, Cc1a inhibited I Ba mediated by high voltage-activated CaV channels but did not affect low voltage-activated T-type CaV channels. Cc1a exhibited weak activity at NaV1.5 and NaV1.7 voltage-gated sodium (NaV) channels stably expressed in mammalian HEK or CHO cells, respectively. Experiments with modified Cc1a peptides, truncated at the N-terminus (ΔG1–E5) or C-terminus (ΔW35–V39), demonstrated that the N- and C-termini are important for voltage-gated ion channel modulation. We conclude that Cc1a represents a novel pharmacological tool for probing the structure and function of L-type CaV channels. [Copyright &y& Elsevier]