Browsing by Author "Bansal, PS"
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- ItemAnalgesic ω-conotoxins CVIE and CVIF selectively and voltage-dependently block recombinant and native n-type calcium channels(American Society for Pharmacology and Experimental Therapeutics (ASPET), 2010-02-01) Berecki, G; Motin, L; Haythornthwaite, A; Vink, S; Bansal, PS; Drinkwater, R; Wang, CI; Moretta, M; Lewis, RJ; Alewood, PF; Christie, MJ; Adams, DJNeuronal (N)-type Ca2+ channel-selective ω-conotoxins have emerged as potential new drugs for the treatment of chronic pain. In this study, two new ω-conotoxins, CVIE and CVIF, were discovered from a Conus catus cDNA library. Both conopeptides potently displaced 125I-GVIA binding to rat brain membranes. In Xenopus laevis oocytes, CVIE and CVIF potently and selectively inhibited depolarization-activated Ba2+ currents through recombinant N-type (α1B-b/α2δ1/β3) Ca2+ channels. Recovery from block increased with membrane hyperpolarization, indicating that CVIE and CVIF have a higher affinity for channels in the inactivated state. The link between inactivation and the reversibility of ω-conotoxin action was investigated by creating molecular diversity in β subunits: N-type channels with β2a subunits almost completely recovered from CVIE or CVIF block, whereas those with β3 subunits exhibited weak recovery, suggesting that reversibility of the ω-conotoxin block may depend on the type of β-subunit isoform. In rat dorsal root ganglion sensory neurons, neither peptide had an effect on low-voltage-activated T-type channels but potently and selectively inhibited high voltage-activated N-type Ca2+ channels in a voltage-dependent manner. In rat spinal cord slices, both peptides reversibly inhibited excitatory monosynaptic transmission between primary afferents and dorsal horn superficial lamina neurons. Homology models of CVIE and CVIF suggest that ω-conotoxin/voltage-gated Ca2+ channel interaction is dominated by ionic/electrostatic interactions. In the rat partial sciatic nerve ligation model of neuropathic pain, CVIE and CVIF (1 nM) significantly reduced allodynic behavior. These N-type Ca2+ channel-selective ω-conotoxins are therefore useful as neurophysiological tools and as potential therapeutic agents to inhibit nociceptive pain pathways. © 2010, American Society for Pharmacology and Experimental Therapeutics (ASPET)
- ItemCyclization of the antimicrobial peptide gomesin with native chemical ligation: influences on stability and bioactivity(Wiley-V C H Verlag, 2013-03-18) Chan, LY; Zhang, VM; Huang, YH; Waters, NC; Bansal, PS; Craik, DJ; Daly, NLGomesin is an 18-residue peptide originally isolated from the hemocytes of the Brazilian spider Acanthoscurria gomesiana. A broad spectrum of bioactivities have been attributed to gomesin, including in vivo and in vitro cytotoxicity against tumour cells, antimicrobial, antifungal, anti-Leishmania and antimalarial effects. Given the potential therapeutic applications of gomesin, it was of interest to determine if an engineered version with a cyclic backbone has improved stability and bioactivity. Cyclization has been shown to confer enhanced stability and activity to a range of bioactive peptides and, in the case of a cone snail venom peptide, confer oral activity in a pain model. The current study demonstrates that cyclization improves the in vitro stability of gomesin over a 24 hour time period and enhances cytotoxicity against a cancer cell line without being toxic to a noncancerous cell line. In addition, antimalarial activity is enhanced upon cyclization. These findings provide additional insight into the influences of backbone cyclization on the therapeutic potential of peptides. © 2013, Wiley-VCH Verlag.
- ItemPlatypus venom: source of novel compounds(CSIRO Publishing, 2009-10) Koh, JMS; Bansal, PS; Torres, AM; Kuchel, PWAn anatomical feature of the platypus (Ornithorhynchus anatinus) that is seen in only one other mammal, the echidna, is that the male has a crural glandular system that produces venom that is used for defence and territorial-breeding functions; whether the echidna is similarly venomous is not yet established. Platypus venom contains many novel proteins and peptides that are different from those in reptilian venom. It also causes pain and symptoms that are not experienced by any other kind of envenomation. Five types of proteins and peptides have been isolated and identified from platypus venom, namely: defensin-like peptides (DLPs); Ornithorhynchus venom C-type natriuretic peptides (OvCNPs); Ornithorhynchus nerve growth factor; hyaluronidase; and L-to-D-peptide isomerase. The structures of DLPs and OvCNPs have already been studied and they are very similar to b-defensin-12 and mammalian C-type natriuretic peptides, respectively. A special mammalian L-to-D-peptide isomerase that is responsible for interconverting the L-and D-peptide isomers is also found in platypus venom. Isomerase activity has recently been discovered in platypus tissues other than the venom gland. It is possible that similar kinds of enzymes might exist in other mammals and play important, as yet unknown, biological roles. Considering the fact that some animal venoms have already been widely used in pharmaceutical applications, research into platypus venom may lead to the discovery of new molecules and potent drugs that are useful biomedical tools. © 2009, CSIRO Publishing
- ItemPore domain outer helix contributes to both activation and inactivation of the hERG K+ channel(American Society for Biochemistry and Molecular Biology, 2009-01-09) Ju, P; Pages, G; Riek, RP; Chen, PC; Torres, AM; Bansal, PS; Kuyucak, S; Kuchel, PW; Vandenberg, JIIon flow in many voltage-gated K+ channels (VGK), including the (human ether-a-go-go-related gene) hERG channel, is regulated by reversible collapse of the selectivity filter. hERG channels, however, exhibit low sequence homology to other VGKs, particularly in the outer pore helix (S5) domain, and we hypothesize that this contributes to the unique activation and inactivation kinetics in hERG K+ channels that are so important for cardiac electrical activity. The S5 domain in hERG identified by NMR spectroscopy closely corresponded to the segment predicted by bioinformatics analysis of 676 members of the VGK superfamily. Mutations to approximately every third residue, from Phe(551) to Trp(563), affected steady state activation, whereas mutations to approximately every third residue on an adjacent face and spanning the entire S5 segment perturbed inactivation, suggesting that the whole span of S5 experiences a rearrangement associated with inactivation. We refined a homology model of the hERG pore domain using constraints from the mutagenesis data with residues affecting inactivation pointing in toward S6. In this model the three residues with maximum impact on activation (W563A, F559A, and F551A) face out toward the voltage sensor. In addition, the residues that when mutated to alanine, or from alanine to valine, that did not express (Ala(561), His(562), Ala(565), Trp(568), and Ile(571)), all point toward the pore helix and contribute to close hydrophobic packing in this region of the channel. © 2009, American Society for Biochemistry and Molecular Biology
- ItemStructural effects of the antimicrobial peptide maculatin 1.1 on supported lipid bilayers(Springer, 2013-01-01) Fernandez, DI; Brun, AP; Lee, TH; Bansal, PSThe interactions of the antimicrobial peptide maculatin 1.1 (GLFGVLAKVAAHVVPAIAEHF-NH2) with model phospholipid membranes were studied by use of dual polarisation interferometry and neutron reflectometry and dimyristoylphosphatidylcholine (DMPC) and mixed DMPC–dimyristoylphosphatidylglycerol (DMPG)-supported lipid bilayers chosen to mimic eukaryotic and prokaryotic membranes, respectively. In DMPC bilayers concentration-dependent binding and increasing perturbation of bilayer order by maculatin were observed. By contrast, in mixed DMPC–DMPG bilayers, maculatin interacted more strongly and in a concentration-dependent manner with retention of bilayer lipid order and structure, consistent with pore formation. These results emphasise the importance of membrane charge in mediating antimicrobial peptide activity and emphasise the importance of using complementary methods of analysis in probing the mode of action of antimicrobial peptides.© 2013, Springer.
- ItemStructure of the pore-helix of the hERG K+ channel(Springer, 2009-12) Pages, G; Torres, AM; Ju, P; Bansal, PS; Alewood, PF; Kuchel, PW; Vandenberg, JIThe hERG K+ channel undergoes rapid inactivation that is mediated by 'collapse' of the selectivity filter, thereby preventing ion conduction. Previous studies have suggested that the pore-helix of hERG may be up to seven residues longer than that predicted by homology with channels with known crystal structures. In the present work, we determined structural features of a peptide from the pore loop region of hERG (residues 600-642) in both sodium dodecyl sulfate (SDS) and dodecyl phosphocholine (DPC) micelles using NMR spectroscopy. A complete structure calculation was done for the peptide in DPC, and the localization of residues inside the micelles were analysed by using a water-soluble paramagnetic reagent with both DPC and SDS micelles. The pore-helix in the hERG peptide was only two-four residues longer at the N-terminus, compared with the pore helices seen in the crystal structures of other K+ channels, rather than the seven residues suggested from previous NMR studies. The helix in the peptide spanned the same residues in both micellar environments despite a difference in the localization inside the respective micelles. To determine if the extension of the length of the helix was affected by the hydrophobic environment in the two types of micelles, we compared NMR and X-ray crystallography results from a homologous peptide from the voltage gated potassium channel, KcsA. © 2009, Springer.