10 research outputs found
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
No full textConformational diversity or
“shapeshifting” in cyclic peptide natu-
ral products can, in principle, confer a
single molecular entity with the proper-
ty 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 disul-
fide moiety. The natural sequences
derived from
Conus inscriptus
,
GCV
D
LYPWC* (In936) and
Conus lor-
oisii
, GCP
D
WDPWC* (Lo959) differ in
the number of proline residues within
the macrocyclic ring. Structural charac-
terisation of distinct conformational
states arising from
cis
–
trans
equilibria
about Xxx–Pro bonds is reported. Iso-
merisation about the C2–P3 bond is
observed in the case of Lo959 and
about the Y5–P6 bond in In936. Evi-
dence is presented for as many as four
distinct species in the case of the syn-
thetic analogue V3P In936. The Tyr-
Pro-Trp segment in In936 is character-
ised by distinct sidechain orientations
as a consequence of aromatic/proline
interactions as evidenced by specific
sidechain–sidechain nuclear Overhaus-
er effects and ring current shifted
proton chemical shifts. Molecular dy-
namics simulations suggest that Tyr5
and Trp7 sidechain conformations are
correlated and depend on the geometry
of the Xxx–Pro bond. Thermodynamic
parameters are derived for the
cis
$
trans
equilibrium for In936. Studies on
synthetic analogues provide insights
into the role of sequence effects in
modulating isomerisation about Xxx–
Pro bonds.Peer ReviewedPostprint (published version
Characterization of contryphans from Conus loroisii and Conus amadis that target calcium channels
No full textDistinctly different effects of two closely related contryphans have been demonstrated on voltage-activated channels. The peptides Lo959 and Am975 were isolated from Conus loroisii, a vermivorous marine snail and Conus amadis, a molluscivore, respectively. The sequences of Lo959 and Am975 were deduced by mass spectrometric sequencing (MALDI-MS/MS) and confirmed by chemical synthesis. The sequences of Lo959, and Am975, (O: 4-trans-hydroxyproline: Hyp), differ only at residue 3; Pro in Lo959, Hyp in Am975, which is identical to contryphan-P, previously isolated from Conus purpurascens, a piscivore; while Lo959 is a novel peptide. Both Lo959 and Am975 undergo slow conformational interconversion under reverse-phase chromatographic conditions, a characteristic feature of all contryphans reported thus far. Electrophysiological studies performed using dorsal root ganglion neurons reveal that both peptides target high voltage-activated channels. While Lo959 increases the current, Am975 causes inhibition. The results establish that subtle sequence effects, which accompany post-translational modifications in Conus peptides, can have dramatic effects on target ion channels
Conformational Analysis of a 20-Membered Cyclic Peptide Disulfide from Conus virgo with a WPW Segment: Evidence for an Aromatic-Proline Sandwich
No full textA 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. A detailed analysis of the conformation in solution is reported for Vi804 and a synthetic analogue, (CIWPWC)-W-D ((D)W3-Vi804), in order to establish the structure of the novel WPW motif, which occurs in the context of a 20-membered macrocyclic disulfide. Vi804 exists exclusively in the cis W3P4 conformer in water and methanol, whereas (D)W3-Vi804 occurs exclusively as the trans conformer. NMR spectra revealed a W3P4 typeVI turn in Vi804 and a typeII turn in the analogue peptide, (D)W3-Vi804. The extremely high-field chemical shifts of the proline ring protons, together with specific nuclear Overhauser effects, are used to establish a conformation in which the proline ring is sandwiched between the flanking Trp residues, which emphasises a stabilising role for the aromatic-proline interactions, mediated predominantly by dispersion forces
Synthesis of Peptide Cysteine Dimedone Using Fmoc‐Cys(Dmd)‐OH: Glutathione Cysteine Dimedone as a Probe in Investigating the Sulfenic Acid Mediated Oxidation of Glutathione
No full text
Novel peptides of therapeutic promise from Indian conidae
No full textHighly structured small peptides are the major toxic constituents of the venom of cone snails, a family of widely distributed predatory marine molluscs. These animals use the venom for rapid prey immobilization. The peptide components in the venom target a wide variety of membrane-bound ion channels and receptors. Many have been found to be highly selective for a diverse range of mammalian ion channels and receptors associated with pain-signaling pathways. Their small size, structural stability, and target specificity make them attractive pharmacologic agents. A select number of laboratories mainly from the United States, Europe, Australia, Israel, and China have been engaged in intense drug discovery programs based on peptides from a few snail species. Coastal India has an estimated 20-30% of the known cone species; however, few serious studies have been reported so far. We have begun a comprehensive program for the identification and characterization of peptides from cone snails found in Indian Coastal waters. This presentation reviews our progress over the last 2 years. As expected from the evolutionary history of these venom components, our search has yielded novel peptides of therapeutic promise from the new species that we have studied
Pruning nature: Biodiversity-derived discovery of novel sodium channel blocking conotoxins from Conus bullatus
No full textThe Redox-Active Conopeptide Derived from the Venom Duct Transcriptome of Conus lividus Assists in the Oxidative Folding of Conotoxin
No full textDe Novo Sequencing and Disulfide Mapping of a Bromotryptophan-Containing Conotoxin by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry
No full textT-1-family conotoxins belong to the T-superfamily and are composed of 10-17 amino acids. They share a common cysteine framework and disulfide connectivity and exhibit unusual posttranslational modifications, such as tryptophan bromination, glutamic acid carboxylation, and threonine glycosylation. We have isolated and characterized a novel peptide, Mo1274, containing 11 amino acids, that shows the same cysteine pattern, -CC-CC, and disulfide linkage as those of the T-1-family members. The complete sequence, , in which denotes bromotryptophan, was derived from MS-based de novo sequencing. The FT-ICR MS/MS techniques of electron capture dissociation (ECD), infrared multiphoton dissociation, and collision-induced dissociation served to detect and localize the tryptophan bromination. The bromine contributes a distinctive isotopic distribution in all fragments that contain bromotryptophan. ECD fragmentation results in the loss of bromine and return to the normal isotopic distribution. Disulfide connectivity of Mo1274, between cysteine pairs 1-3 and 2-4, was determined by mass spectrometry in combination with chemical derivatization employing tris(2-carboxyethyl)-phosphine, followed by differential alkylation with Nethylmaleimide and iodoacetamide. The ECD spectra of the native and partially modified peptide reveal a loss of bromine in a process that requires the presence of a disulfide bond
