Incorporation of post-translational modified amino acids as an approach to increase both chemical and biological diversity of conotoxins and conopeptides

Abstract

Bioactive peptides from Conus venom contain a natural abundance of post-translational modifications that affect their chemical diversity, structural stability, and neuroactive properties. These modifications have continually presented hurdles in their identification and characterization. Early endeavors in their analysis relied on classical biochemical techniques that have led to the progressive development and use of novel proteomic-based approaches. The critical importance of these post-translationally modified amino acids and their specific assignment cannot be understated, having impact on their folding, pharmacological selectivity, and potency. Such modifications at an amino acid level may also provide additional insight into the advancement of conopeptide drugs in the quest for precise pharmacological targeting. To achieve this end, a concerted effort between the classical and novel approaches is needed to completely elucidate the role of post-translational modifications in conopeptide structure and dynamics. This paper provides a reflection in the advancements observed in dealing with numerous and multiple post-translationally modified amino acids within conotoxins and conopeptides and provides a summary of the current techniques used in their identification.

t‐boc synthesis of huwentoxin‐i through native chemical ligation incorporating a trifluoromethanesulfonic acid cleavage strategy

“…Random oxidation of the ligated HwTx‐I produced 10 out of the 16 possible disulfide isomers (Supporting Information Figure S2). Our goal here was to produce as many isomers as possible and to examine the potential for alternative structures that could have demonstrated bioactivity.…”

Structural and Functional Analyses of Cone Snail Toxins

“…These facts show that post-translational modifications in α-conotoxins can interfere in conotoxin/nAChR interactions. Indeed, it was suggested that amidation promotes native folding in this toxin group, leading to their selectivity [26]. Previous experiments showed that the proline from the m -loop and C-terminal amidation in α- and χ-conotoxins act as conformational switches [69].…”

“…Conotoxins’ structural properties seem to be important for target interaction [25]. Importantly, other features are present in natural conotoxins such as the location of key amino acids on their primary sequence [5] and post-translational modifications, including amidation, sulfation, pyroglutamylation, γ-carboxylation, hydroxylation, O-glycosylation, and bromination [26]. On the whole, these features must be considered when analyzing conotoxin/target interaction.…”

Conotoxins and their Regulatory Considerations

“…Conotoxins contain numerous Post-translational Modifications [17]. These PTMs are responsible for phyla and receptor selectivity.…”

“…These structural features are stabilized by disulfide bonds generated from the abundance of cysteine moieties in its primary structure [1,4]. Interestingly, these Cys residues are found in predictable locations within a conotoxin's sequence, giving rise to loops of known amino acid lengths, which influence their bioactivity [4,5]. Conotoxins can contain anywhere from one to five disulfide bonds which typically produce intramolecular connections [6].…”