Structure-aided function assignment to the transcriptomic conopeptide Am931.

Implementation of the next-generation technologies for gene sequencing of venom duct transcriptome has provided a large number of peptide sequences of marine cone snails. Emerging technologies on computational platforms are now rapidly evolving for the accurate predictions of the 3D structure of the polypeptide using the primary sequence. The current report aims to integrate the information derived from these two technologies to develop the concept of structure-aided function assignment of Conus peptides.

Antimicrobial and antitumor properties of anuran peptide temporin-SHf induce apoptosis in A549 lung cancer cells.

Temporin-SHf is a linear, ultra-short, hydrophobic, α-helix, and phe-rich cationic antimicrobial peptide. The antitumor activities and mechanism of temporin-SHf-induced cancer cell death are unknown. The temporin-SHf was synthesized by solid-phase Fmoc chemistry and antimicrobial and antitumor activities were investigated.

Oxidative Folding Catalysts of Conotoxins Derived from the Venom Duct Transcriptome of and .

Two novel redox conopeptides with proline residues outside and within the active site disulfide loop were derived from the venom duct transcriptome of the marine cone snails and . Mature peptides with possible post-translational modification of 4-trans-hydroxylation of proline, namely, Fr874, Fr890[P1O], Fr890[P2O], Fr906, Am1038, and Am1054, have been chemically synthesized and characterized using mass spectrometry. The estimated reduction potential of cysteine disulfides of synthetic peptides varied from -298 to -328 mV, similar to the active site cysteine disulfide motifs of the redox family of proteins.

Peptide Cysteine Thiols Act as Photostabilizer of Avobenzone through Stabilizing the Transition State of Keto-Enol Tautomerization.

Photostabilizers have been used to impart stability to an FDA-approved chemical UV-A filter avobenzone against the UV-A radiations and sunlight. The thiol group of glutathione plays a critical role in imparting the photostabilization activity of glutathione on avobenzone. The current report aims to evaluate the photostabilization activity of multiple thiols containing cysteine peptides on avobenzone.

Significance of D- tryptophan in Contryphan-Ar1131 Conus peptide: Oxidative folding, trypsin binding, and photostabilization activity.

Distinct differences have been observed between L-tryptophan and D-tryptophan containing contryphan-Ar1131 in oxidative folding, trypsin binding, and photostabilization activity on avobenzone. [W] contryphan-Ar1131 and [w] contryphan-Ar1131 were chemically synthesized and characterized using RP-HPLC and mass spectrometry. Structural differences due to the change of configuration of tryptophan were evident from the optimized structures of contryphan-Ar1131 using density functional theory (DFT).

Antitumor activity of Tigerinin-1: Necroptosis mediates toxicity in A549 cells.

Background: Tigerinins are antimicrobial peptides (AMPs) derived from the skin secretions of the Indian bullfrog Hoplobatrachus tigerinus.

Methods: Tigerinin-1 (FCTMIPIPRCY-Am) peptide was synthesized by solid-phase Fmoc chemistry and investigated its antitumor activities.

Results: Tigerinin-1 was cytotoxic to human cancer cells.

Conformational change due to replacement of disulfide with selenosulfide and diselenide in dipeptide vicinal cysteine loop.

Replacement of disulfide bridges with diselenide bridges is increasingly common to improve the stability, foldability, and structural refinement of the cysteine-rich polypeptides. Even though the global structural features are similar due to the replacement of disulfide with diselenide, the local conformational differences have been reported in a few polypeptides. The current report has used the constrained vicinal cysteine disulfide as the model to access the influence of the replacement of disulfides with diselenide on the local conformations.

Gram-Scale Synthesis of 1,8-Naphthyridines in Water: The Friedlander Reaction Revisited.

The products of the Friedlander reaction, i.e., 1,8-naphthyridines, have far-reaching impacts in materials science, chemical biology, and medicine.

The Redox-Active Conopeptide Derived from the Venom Duct Transcriptome of Assists in the Oxidative Folding of Conotoxin.

The tetrapeptides Li504 and Li520, differing in the modification of the 4--hydroxylation of proline, are novel conopeptides derived from the venom duct transcriptome of the marine cone snail . These predicted mature peptides are homologous to the active site motif of oxidoreductases that catalyze the oxidation, reduction, and rearrangement of disulfide bonds in peptides and proteins. The estimated reduction potential of the disulfide of Li504 and Li520 is within the range of disulfide reduction potentials of oxidoreductases, indicating that they may catalyze the oxidative folding of conotoxins.

Ligand-induced transition in conformations of vicinal cysteine disulfides in proteins.

Vicinal cysteine disulfides are thought to be associated with specific conformations of cysteine disulfides due to the restricted rotation of single bonds in an eight-membered cyclic disulfide loop. Conformations of vicinal cysteine disulfides are analyzed using χ , χ , χ , χ ', χ ' torsion angles in the crystal structures of proteins retrieved from Protein Data Bank (PDB). 85% of vicinal disulfides have (+, -)LHStaple conformation with trans configuration of the peptide bond and 9% have (-, -)RHStaple conformation with cis configured peptide bond.

Characterization of (Boc-Cys/Sec-NHMe) and (Boc-Cys/Sec-OMe) : Evidence of local conformational difference between disulfide and diselenide.

Conformations of disulfide and diselenide were compared in (Boc-Cys/Sec-NHMe) and (Boc-Cys/Sec-OMe) using X-ray crystallography, nuclear magnetic resonance (NMR) spectroscopy, density functional theory (DFT), and circular dichroism (CD) spectroscopy. Conformations of disulfide/diselenide in polypeptides are defined based on the sign of side chain torsion angle χ (-CH -S/Se-S/Se-CH -); negative indicates left-handed and positive indicates right-handed orientation. In the crystals of (Boc-Cys-OMe) and (Boc-Sec-OMe) , the disulfide exhibits a left-handed and the diselenide a right-handed orientation.

Disulfide engineering on temporin-SHf: Stabilizing the bioactive conformation of an ultra-short antimicrobial peptide.

In Silico searching for short antimicrobial peptides has revealed temporin-SHf as the short (8AA), hydrophobic, broad spectrum, and natural antimicrobial peptide. Important drawback associated with temporin-SHf is the susceptibility of its bioactive conformation for denaturation and proteolytic degradation. In the current report, disulfide engineering strategy has been adopted to improve the stability of bioactive conformation of temporin-SHf.

Glutathione as a photo-stabilizer of avobenzone: an evaluation under glass-filtered sunlight using UV-spectroscopy.

Avobenzone is the most widely used UVA filter in sunscreen lotion and it is prone to degradation in the presence of sunlight/UV radiation. To overcome the photo-instability of avobenzone, various photostabilizers have been used as additives, including antioxidants such as vitamin C, vitamin E, and ubiquinone. In the present study, the well known antioxidant, glutathione, was evaluated for protecting avobenzone from photodegradation in the presence of glass-filtered sunlight.

Conformations of cysteine disulfides of peptide toxins: Advantage of differentiating forward and reverse asymmetric disulfide conformers.

Conformations of cysteine disulfides were analyzed in X-ray, nuclear magnetic resonance (NMR), and co-crystal structures of peptide toxins retrieved from Protein Data Bank. The parameters side chain torsional angles, disulfide strain energy, interatomic Cα/Cβ distances, and Ramachandran angles were used as probes to derive conformational features of cysteine disulfides. Schmidt, Ho, and Hogg ( 2006 ) Allosteric disulfide bonds.

Electron transfer dissociation of synthetic and natural peptides containing lanthionine/methyllanthionine bridges.

Rationale: The modes of cleavage of lanthionine/methyllanthionine bridges under electron transfer dissociation (ETD) were investigated using synthetic and natural lantipeptides. Knowledge of the mass spectrometric fragmentation of lanthionine/methyllanthionine bridges may assist in the development of analytical methods for the rapid discovery of new lantibiotics. The present study strengthens the advantage of ETD in the characterization of posttranslational modifications of peptides and proteins.

Structural space of intramolecular peptide disulfides: Analysis of peptide toxins retrieved from venomous peptide databases.

Structural space of intramolecular peptide disulfides is the combination of arrangement of even number of cysteine residues in single polypeptide and the disulfide isomers resulting from differential connectivity between cysteine residues. In the current report, we are documenting theoretical analysis and derivation of general formula [2×4] to predict possible distinct cysteine patterns for given 'n' even number of cysteine residues in a sequence. Combined formula of predicting distinct cysteine patterns and different disulfide isomers can be used to deduce the truly available structural space of intramolecular peptide disulfides, which may be used in structural analysis of disulfide rich peptides and proteins.

Evaluation of hexane and ethyl acetate extracts of the sponge Jaspis diastra collected from Mauritius Waters on HeLa cells.

Objectives: Based on previous screening results, the cytotoxic effect of the hexane (JDH) and ethyl acetate extracts (JDE) of the marine sponge Jaspis diastra were evaluated on HeLa cells and the present study aimed at determining their possible mechanism of cell death.

Methods: Nuclear staining, membrane potential change, flow cytometry analysis of cell cycle distribution and annexin V staining were undertaken to investigate the effects of JDE and JDH. Electrospray ionization mass spectrometry (ESI-MS) and nuclear magnetic resonance were used to characterize an isolated bioactive molecule.

Conformational analysis of a 20-membered cyclic peptide disulfide from Conus virgo with a WPW segment: evidence for an aromatic-proline sandwich.

A novel peptide containing a single disulfide bond, CIWPWC (Vi804), has been isolated and characterised from the venom of the marine cone snail, Conus virgo. A precursor polypeptide sequence derived from complementary DNA, corresponding to the M-superfamily conotoxins, has been identified. The identity of the synthetic and natural peptide sequence has been established.

Conformational diversity in contryphans from Conus venom: cis-trans isomerisation and aromatic/proline interactions in the 23-membered ring of a 7-residue peptide disulfide loop.

Conformational diversity or "shapeshifting" in cyclic peptide natural products can, in principle, confer a single molecular entity with the property of binding to multiple receptors. Conformational equilibria have been probed in the contryphans, which are peptides derived from Conus venom possessing a 23-membered cyclic disulfide moiety. The natural sequences derived from Conus inscriptus, GCV(D)LYPWC* (In936) and Conus loroisii, GCP(D)WDPWC* (Lo959) differ in the number of proline residues within the macrocyclic ring.

Rapid mass spectrometric determination of disulfide connectivity in peptides and proteins.

Disulfide crosslinks are ubiquitous in natural peptides and proteins, providing rigidity to polypeptide scaffolds. The assignment of disulfide connectivity in multiple crosslinked systems is often difficult to achieve. Here, we show that rapid unambiguous characterisation of disulfide connectivity can be achieved through direct mass spectrometric CID fragmentation of the disulfide intact polypeptides.

Dissecting a role of evolutionary-conserved but noncritical disulfide bridges in cysteine-rich peptides using ω-conotoxin GVIA and its selenocysteine analogs.

Conotoxins comprise a large group of peptidic neurotoxins that use diverse disulfide-rich scaffolds. Each scaffold is determined by an evolutionarily conserved pattern of cysteine residues. Although many structure-activity relationship studies confirm the functional and structural importance of disulfide crosslinks, there is growing evidence that not all disulfide bridges are critical in maintaining activities of conotoxins.

Conantokins derived from the Asprella clade impart conRl-B, an N-methyl d-aspartate receptor antagonist with a unique selectivity profile for NR2B subunits.

Using molecular phylogeny has accelerated the discovery of peptidic ligands targeted to ion channels and receptors. One clade of venomous cone snails, Asprella, appears to be significantly enriched in conantokins, antagonists of N-methyl d-aspartate receptors (NMDARs). Here, we describe the characterization of two novel conantokins from Conus rolani, including conantokin conRl-B that has shown an unprecedented selectivity for blocking NMDARs that contain NR2B subunits.

Disulfide-Depleted Selenoconopeptides: a Minimalist Strategy to Oxidative Folding of Cysteine-Rich Peptides.

Despite the therapeutic promise of disulfide-rich, peptidic natural products, their discovery and structure/function studies have been hampered by inefficient oxidative folding methods for their synthesis. Here we report that converting the three disulfide-bridged mu-conopeptide KIIIA into a disulfide-depleted selenoconopeptide (by removal of a noncritical disulfide bridge and substitution of a disulfide- with a diselenide-bridge) dramatically simplified its oxidative folding while preserving the peptide's ability to block voltage-gated sodium channels. The simplicity of synthesizing disulfide-depleted selenopeptide analogs containing a single disulfide bridge allowed rapid positional scanning at Lys7 of mu-KIIIA, resulting in the identification of K7L as a mutation that improved the peptide's selectivity in blocking a neuronal (Na(v)1.