Ero1-Mediated Reoxidation of Protein Disulfide Isomerase Accelerates the Folding of Cone Snail Toxins

Disulfide-rich peptides are highly abundant in nature and their study has provided fascinating insight into protein folding, structure and function. Venomous cone snails belong to a group of organisms that express one of the largest sets of disulfide-rich peptides (conotoxins) found in nature. The diversity of structural scaffolds found for conotoxins suggests that specialized molecular adaptations have evolved to ensure their efficient folding and secretion. We recently showed that canonical protein disulfide isomerase (PDI) and a conotoxin-specific PDI (csPDI) are ubiquitously expressed in the venom gland of cone snails and play a major role in conotoxin folding. Here, we identify cone snail endoplasmic reticulum oxidoreductin-1 (Conus Ero1) and investigate its role in the oxidative folding of conotoxins through reoxidation of cone snail PDI and csPDI. We show that Conus Ero1 preferentially reoxidizes PDI over csPDI, suggesting that the reoxidation of csPDI may rely on an Ero1-independent molecular pathway. Despite the preferential reoxidation of PDI over csPDI, the combinatorial effect of Ero1 and csPDI provides higher folding yields than Ero1 and PDI. We further demonstrate that the highest in vitro folding rates of two model conotoxins are achieved when all three enzymes are present, indicating that these enzymes may act synergistically. Our findings provide new insight into the generation of one of the most diverse classes of disulfide-rich peptides and may improve current in vitro approaches for the production of venom peptides for pharmacological studies

Characterization of the Conus bullatus genome and its venom-duct transcriptome

<p>Abstract</p> <p>Background</p> <p>The venomous marine gastropods, cone snails (genus <it>Conus</it>), inject prey with a lethal cocktail of conopeptides, small cysteine-rich peptides, each with a high affinity for its molecular target, generally an ion channel, receptor or transporter. Over the last decade, conopeptides have proven indispensable reagents for the study of vertebrate neurotransmission. <it>Conus bullatus </it>belongs to a clade of <it>Conus </it>species called <it>Textilia</it>, whose pharmacology is still poorly characterized. Thus the genomics analyses presented here provide the first step toward a better understanding the enigmatic <it>Textilia </it>clade.</p> <p>Results</p> <p>We have carried out a sequencing survey of the <it>Conus bullatus </it>genome and venom-duct transcriptome. We find that conopeptides are highly expressed within the venom-duct, and describe an <it>in silico </it>pipeline for their discovery and characterization using RNA-seq data. We have also carried out low-coverage shotgun sequencing of the genome, and have used these data to determine its size, genome-wide base composition, simple repeat, and mobile element densities.</p> <p>Conclusions</p> <p>Our results provide the first global view of venom-duct transcription in any cone snail. A notable feature of <it>Conus bullatus </it>venoms is the breadth of A-superfamily peptides expressed in the venom duct, which are unprecedented in their structural diversity. We also find SNP rates within conopeptides are higher compared to the remainder of <it>C. bullatus </it>transcriptome, consistent with the hypothesis that conopeptides are under diversifying selection.</p

Reversible phosphine binding to palladium arylazooximates: correlation of equilibrium constants with cone angles

This article does not have an abstract

Arylazo-oximates of ortho-palladated azobenzenes: synthesis, isomerism, and redox behaviour

The synthesis and characterisation of new planar mixed species of the type [PdLA](A =ortho-metallated azobenzene or its substituted derivative) is achieved by splitting the halogeno-bridge in [Pd₂Cl₂A₂] by arylazo-oximes (HL). Triphenylphosphine cleaves the Pd-N(azo) bond in the PdL fragment, giving [PdLA(PPh₃)]. Many of the [PdLA] species occur as isomeric mixtures whose compositions have been established using ¹H n.m.r. data. The isomerism which originates from different modes of ortho-metallation of A is carried over to [PdLA] from the precursor complex [Pd₂Cl₂A₂]. A simple and accurate 1H n.m.r. method of isomer analysis in [Pd₂Cl₂A₂] is described. Substituent effects on isomer population are consistent with the electrophilic nature of the palladation reaction but steric effects also play dominant roles. The electrochemistry of [PdLA] has been thoroughly examined using cyclic voltammetry. Three couples are observed near –0.8, –1.2, and –1.5 V vs. standard calomel electrode, in acetonitrile. The first two couples correspond to successive one-electron reductions of the azo-functions of L and A respectively. The third couple is due to two-electron metal reduction

Elucidation of the molecular envenomation strategy of the cone snail <it>Conus geographus</it> through transcriptome sequencing of its venom duct

Abstract Background The fish-hunting cone snail, Conus geographus, is the deadliest snail on earth. In the absence of medical intervention, 70% of human stinging cases are fatal. Although, its venom is known to consist of a cocktail of small peptides targeting different ion-channels and receptors, the bulk of its venom constituents, their sites of manufacture, relative abundances and how they function collectively in envenomation has remained unknown. Results We have used transcriptome sequencing to systematically elucidate the contents the C. geographus venom duct, dividing it into four segments in order to investigate each segment’s mRNA contents. Three different types of calcium channel (each targeted by unrelated, entirely distinct venom peptides) and at least two different nicotinic receptors appear to be targeted by the venom. Moreover, the most highly expressed venom component is not paralytic, but causes sensory disorientation and is expressed in a different segment of the venom duct from venoms believed to cause sensory disruption. We have also identified several new toxins of interest for pharmaceutical and neuroscience research. Conclusions Conus geographus is believed to prey on fish hiding in reef crevices at night. Our data suggest that disorientation of prey is central to its envenomation strategy. Furthermore, venom expression profiles also suggest a sophisticated layering of venom-expression patterns within the venom duct, with disorientating and paralytic venoms expressed in different regions. Thus, our transcriptome analysis provides a new physiological framework for understanding the molecular envenomation strategy of this deadly snail.</p

Liquid Crystalline Aryltriazene-1-Oxides with Two Ester Units: Synthesis, Characterisation, Structure and Thermal Properties

A new series of mesogenic triazene-1-oxides, C6H5-N(O)=N-NH-C6H4-C(O)-O- C6H4-O-(O)C-C6H4-OR (1, R=n-alkyl group from CH3 to C14H29), was designed and synthesised. All members of this new series were characterised on the basis of spectral and analytical data. The thermotropic liquid crystalline behaviour of the compounds was observed over a wide temperature range using optical microscopy. The mesophase structure was confirmed by a small-angle X-ray diffraction study of a representative member (1k). The molecular structure of compound 1i was determined using the single crystal X-ray diffraction method as a representative case. Dimer formation in the solid state occurs due to intermolecular N-H...O and C-H...O interactions. Intermolecular C-H...&pi interactions were also detected in 1i. The intermolecular hydrogen bonding and intermolecular C-H...p interactions arrange the phenyl triazene-1-oxide fragments of the molecules in layers within the molecular assembly

Novel Synthetic Route to Liquid Crystalline 4,4\u27-Bis(n-Alkoxy) Azoxybenzenes: Spectral Characterisation, Mesogenic Behaviour and Crystal Structure of Two New Members

A simple synthetic method has been developed for the preparation of long-chain 4,4\u27-bis(n-alkoxy)azoxybenzenes by reductive coupling of 4-n-alkoxynitrobenzenes using zinc powder and ammonium chloride in aqueous ethanol medium at ambient temperature. The new method was employed to synthesise known members (n=1-12) of the 4,4\u27-bis(n-alkoxy)azoxybenzene (C n H2n+1OPhN(O)=NPhOC n H2n+1) series and also two hitherto unknown members (n=13-14) of the series. The new compounds were characterised using spectral (IR, UV-visible, 1H NMR and FAB-MS) data. The mesogenic behaviour of both compounds was studied by polarising optical microscopy, differential scanning calorimetry and small-angle X-ray diffraction techniques. The crystal structure of 4,4\u27-bis(n-tetradecyloxy)azoxybenzene was determined using single-crystal X-ray diffraction data. The packing of the molecules in the crystalline state is found to be a precursor to the smectic C phase structure