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Results reveal that the structure of omega-conotoxin TxVII is a 26-residue peptide consisting of a triple-stranded antiparallel beta-sheet with four turns and exposed hydrophobic residues. Data indicate that the hydrophobic residues may interact with the hydrophobic cluster of the L-type calcium channel's alpha1 subunit.

(Omega)-conotoxin TxVII is the only contoxin known to block L-type calcium channels. Unlike other (omega)-conotoxins, TxVII has a sequence characterized by net negative charge and high hydrophobicity. To obtain information needed for structure-activity analysis, TxVII was synthesized chemically and its biological functions analyzed. Results showed that synthetic TxVII could suppress slowly inactivating calcium currents. It was also demonstrated to have a similar effect on synaptic transmission in neurons.

The mastoparans are tetradecapeptide components of wasp venom used as models of receptors bound to G proteins. The interaction between mastoparan X (MP-X) and G proteins is investigated using two-dimensional transferred nuclear Overhauser effect spectroscopy. Prior to the experiment, MP-X was uniformly enriched with isotopic carbon and nitrogen to eliminate the overlap problem. Results indicate that MP-X assumes an amphiphilic alpha helix conformation during the interaction.

Research was conducted to study the expression of the microtubule-associated protein called tau and its fragments in Escherichia coli. The conformation and capacity for aggregation for filamentous structure formation in vitro to provide insights on the pathogenesis of Alzheimer's disease were also studied. Polymerase chain reaction products were determined by T4 polynucleotide kinase while crude protein samples were harvested by SDS-PAGE and electroblotted on a siliconized-glass fiber membrane. Results showed that the C-tail fragments of tau established paired filaments in acidic aqueous solution.

The membrane-mimicking environment of nuclear magnetic resonance spectroscopy was utilized to determine the three-dimensional structure of neurotoxic amyloid beta-protein (Abeta) (25-35) and [N27A-Abeta (25-35)]. The Abeta protein exhibited an alpha-helical structure in the C-terminal region with a disordered stretch in the N-terminal region. However, the mutant form of Abeta exhibited a hydrophobic N-terminal region compared to the hydrophilic N-terminal region of Abeta.

A study determining the three-dimensional structure of omega-conotoxin MVIIA in aqueous solution by using two-dimensional 1H-NMR with annealing calculations shows that the solution conformation of omega-CTX MVIIA is similar to that of omega-CTX GVIA. The molecular structure of omega-conotoxin MVIIA is composed of a short triple-stranded antiparallel beta-sheet. The comparison of structures of the two conotoxins and the structure-function relationships of calcium channel blockers are also discussed.

Barnase is a ribonuclease from Bacillus amyloliquefaciens whose tertiary structure is composed of six modules, M1 to M6. The conformation of the M1 module which comprises the N-terminal fragment of 24 amino acid residues, was determined by circular dichroism spectroscopy. The results showed that M1 assumes a predominantly random coil structure when it is in a monomer state. In contrast, a helical structure is assumed during the multimer state. Such a helical conformation in aqueous solution may be driven by hydrophobic burial forces.

The structure-activity correlates of the sodium channel blocker peptidemu-conotoxin GIIIA was investigated by nuclear magnetic resonance studies and simulated annealing computations of an inactive analog. Results indicate that activity of the peptide was influenced by direct interaction of an important arginine residue with the sodium channel molecules. The active site was characterized by a cluster of arginine, lysine and hydroxyproline which interacts with the receptor site of the sodium channel. The hydroxyl group of hydroxyproline shares a common channel site with tetrodoxin and saxitoxin.

A highly 1,2-trans-selective synthesis of glycosyl boranophosphate derivatives by glycosylation of dimethyl boranophosphate with glycosyl iodides is described. The synthesis of boranophosphate-linked disaccharides and their conversion to the phosphodiester-linked disaccharides are achieved without loss of stereopurity at the anomeric position, demonstrating that the method is useful for preparing diastereopure glycosyl phosphate-containing biomolecules.

A native polyacrylamide gel electrophoresis assay is used to examine the three-dimensional structure and specific binding activities of NCp8 and the NCp8-derived peptides (nucleocapsid (NC) protein of Human Immunodeficiency Virus (HIV) type -2) with SL3. The results provide insight into the RNA recognition mechanism for NCp8 which is different from that of NCp7 (HIV type-1 protein) and the hydrophobic cleft in the second zinc finger that acts as a secondary active domain instead of the [3.sub.10] helix in NCp7.

The three-dimensional structure of the minimal active domain of the HIV-2 nucleocapsid protein NCp8, NCp8-f1, was characterized using high-resolution nuclear magnetic resonance spectroscopy and simulated annealing. Specifically, the structure of the basic amino acid cluster was examined in detail. Experimental results showed that the basic amino acid cluster exhibits a loop-like conformation in which three arginine residues in the cluster and one arginine residue in the zinc finger are found approximately in the same plane of the molecule and are solvent-exposed.

In this study, we successfully synthesized boranophosphate (PB), phosphorothioate (PS), and phosphate (PO) chimeric oligonucleotides (ODNs) as a candidate for the antisense oligonucleotides (ASOs). The PB/PS/PO-ODNs were synthesized utilizing H -boranophosphonate, H -phosphonothioate, and H -phosphonate monomers. Each monomer was condensed with a hydroxy group to create H -boranophosphonate, H -phosphonothioate, and H -phosphonate diester linkages, which were oxidized into PB, PS, and PO linkages in the final stage of the synthesis, respectively. As for condensation of an H -phosphonothioate monomer, regulating chemoselectivity was necessary since the monomer has two nucleophilic centers: S and O atoms. To deal with this problem, we used phosphonium-type condensing reagents, which could control the chemoselectivity. In this strategy, we could synthesize PB/PS/PO oligomers, including a 2'-OMe gapmer-type dodecamer. The physiological and biological properties of the synthesized chimeric ODNs were also evaluated. Insights from the evaluation of physiological and biological properties suggested that the introduction of suitable P -modification and sugar modification at proper sites of ODNs would control the duplex stability, nuclease resistance, RNase H-inducing ability, and one base mismatch discrimination ability, which are critical properties as potent ASOs.

Glycosyl phosphate repeating units can be found in the glycoconjugates of some bacteria and protozoa parasites. These structures and their P-modified analogs are attractive synthetic targets as antimicrobial, antiparasitic, and vaccine agents. However, P-modified glycosyl phosphates exist in different diastereomeric forms due to the chiral phosphorus atoms, whose configuration would highly affect their physiochemical and biochemical properties. In this study, a stereocontrolled method was developed for the synthesis of P-modified glycosyl phosphate repeating units derived from the lipophosphoglycan of Leishmania using the oxazaphospholidine approach. The solid-phase synthesis facilitated the elongation and purification of the glycosyl phosphate derivatives, while two P-modified glycosyl phosphates (boranophosphate and phosphorothioate) were successfully synthesized with up to three repeating units., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

The retinal pigment epithelium (RPE) forms the outer blood-retinal barrier between neural retina and choroid. The RPE has several important vision supporting functions, such as transport mechanisms that may also modify pharmacokinetics in the posterior eye segment. Expression of plasma membrane transporters in the RPE cells has not been quantitated. The aim of this study was to characterize and compare transporter protein expression in the ARPE19 cell line and hfRPE (human fetal RPE) cells by using quantitative targeted absolute proteomics (QTAP). Among 41 studied transporters, 16 proteins were expressed in hfRPE and 13 in ARPE19 cells. MRP1, MRP5, GLUT1, 4F2hc, TAUT, CAT1, LAT1, and MATE1 proteins were detected in both cell lines within 4-fold differences. MPR7, OAT2 and RFC1 were detected in the hfRPE cells, but their expression levels were below the limit of quantification in ARPE19 cells. PCFT was detected in both studied cell lines, but the expression was over 4-fold higher in hfRPE cells. MCT1, MCT4, MRP4, and Na + /K + ATPase were upregulated in the ARPE19 cell line showing over 4-fold differences in the quantitative expression values. Expression levels of 25 transporters were below the limit of quantification in both cell models. In conclusion, we present the first systematic and quantitative study on transporter protein expression in the plasma membranes of ARPE19 and hfRPE cells. Overall, transporter expression in the ARPE19 and hfRPE cells correlated well and the absolute expression levels were similar, but not identical. The presented quantitative expression levels could be a useful basis for further studies on drug permeation in the outer blood-retinal barrier.

Peptide toxins from scorpion venoms constitute the largest group of toxins that target the voltage-gated potassium channel (Kv). Spinoxin (SPX) isolated from the venom of scorpion Heterometrus spinifer is a 34-residue peptide neurotoxin cross-linked by four disulfide bridges. SPX is a potent inhibitor of Kv1.3 potassium channels (IC50 = 63 nM), which are considered to be valid molecular targets in the diagnostics and therapy of various autoimmune disorders and cancers. Here we synthesized 25 analogues of SPX and analyzed the role of each amino acid in SPX using alanine scanning to study its structure-function relationships. All synthetic analogues showed similar disulfide bond pairings and secondary structures as native SPX. Alanine replacements at Lys(23), Asn(26), and Lys(30) resulted in loss of activity against Kv1.3 potassium channels, whereas replacements at Arg(7), Met(14), Lys(27), and Tyr(32) also largely reduced inhibitory activity. These results suggest that the side chains of these amino acids in SPX play an important role in its interaction with Kv1.3 channels. In particular, Lys(23) appears to be a key residue that underpins Kv1.3 channel inhibition. Of these seven amino acid residues, four are basic amino acids, suggesting that the positive electrostatic potential on the surface of SPX is likely required for high affinity interaction with Kv1.3 channels. This study provides insight into the structure-function relationships of SPX with implications for the rational design of new lead compounds targeting potassium channels with high potency.

Secretory phospholipase A2 (sPLA2) and matrix metallopreoteinases (MMPs) are key enzymes involved in rheumatoid arthritis (RA), and their modulation thus represents a potential therapeutic option. On the basis of Escherichia coli radioassay, synthetic peptides were designed and screened for sPLA2 inhibition. The linear peptide, 10f (PIP-18), inhibited the recombinant human synovial sPLA2 activity with an IC50 of 1.19 microM. Not only did the peptide interfere with the function of sPLA2, but it also appeared to inhibit mRNA expression of sPLA2 and various MMPs in IL-1beta-stimulated RA synovial fibroblast (RASF) cultures and thereby the production of the corresponding proteins (>80% inhibition). Nuclear magnetic resonance (NMR), modeling, and docking studies indicate that in solution the peptide exhibits a beta-turn at residues Trp-Asp-Gly-Val and possibly binds to the hydrophobic channel of sPLA2. The results strongly suggest that the modulatory action of peptide 10f may play a major role in counteracting the development of RA.