A C-Terminal Fragment of Chlorotoxin Retains Bioactivity and Inhibits Cell Migration

Chlorotoxin was originally isolated from the venom of the Israeli scorpion Leiurus quinquestriatus, and has potential as a tumor imaging agent based on its selective binding to tumor cells. Several targets have been suggested for chlorotoxin including voltage-gated chloride channels, and it has been shown to have anti-angiogenic activity and inhibit cell migration. The structure of chlorotoxin is stabilized by four disulfide bonds and contains β-sheet and helical structure. Interestingly, the reduced form has previously been shown to inhibit cell migration to the same extent as the wild type, but structural analysis indicates that the reduced form of the peptide does not maintain the native secondary structure and appears unstructured in solution. This lack of structure suggests that a short stretch of amino acids might be responsible for the bioactivity. To explore this hypothesis, we have synthesized fragments of chlorotoxin without disulfide bonds. As expected for such small peptides, NMR analysis indicated that the peptides were unstructured in solution. However, the peptide corresponding to the eight C-terminal residues inhibited cell migration, in contrast to the other fragments. Our results suggest that the C-terminal region plays a critical role in the bioactivity of chlorotoxin

Synthesis, Characterization, X-ray Structural Analysis and Study of Oxidative Properties of Tetraethylammonium Chlorochromate

Tetraethylammonium chlorochromate(VI), Et4N[CrO3Cl] is easily synthesized in nearly quantitative yield using a direct reaction of chromium(VI) oxide and tetraethylammonium chloride and characterized by elemental analysis, IR, UV/Visible, 1H-NMR and 13C-NMR techniques and single-crystal X-ray diffraction analysis (monoclinic system, space group C2(#5), with a = 12.023(3), b = 7.998(2), c = 14.527(4) Å, β = 114.187(4)°, V = 1274.4(6) Å3 and Z = 4). X-ray data determined the CH ··· O hydrogen bond that forms between the ethyl hydrogen of the cation and oxygen of the anion. This compound is a versatile reagent for efficient and selective oxidation of organic substrates, in particular for alcohols to their corresponding aldehydes or ketones, under mild conditions.link_to_subscribed_fulltex

Structural variants of a liver fluke derived granulin peptide potently stimulate wound healing

Granulins are a family of growth factors involved in cell proliferation. The liver-fluke granulin, Ov-GRN-1, isolated from a carcinogenic liver fluke Opisthorchis viverrini, can significantly accelerate wound repair in vivo and in vitro. However, it is difficult to express Ov-GRN-1 in recombinant form at high yield, impeding its utility as a drug lead. Previously we reported that a truncated analogue (Ov-GRN12–35_3s) promotes healing of cutaneous wounds in mice. NMR analysis of this analogue indicates the presence of multiple conformations, most likely as a result of proline cis/trans isomerization. To further investigate whether the proline residues are involved in adopting the multiple confirmations, we have synthesized analogues involving mutation of the proline residues. We have shown that the proline residues have a significant influence on the structure, activity, and folding of Ov-GRN12–35_3s. These results provide insight into improving the oxidative folding yield and bioactivity of Ov-GRN12–35_3s and might facilitate the development of a novel wound healing agent

Development of a Potent Wound Healing Agent Based on the Liver Fluke Granulin Structural Fold

Granulins are a family of protein growth factors that are involved in cell proliferation. An orthologue of granulin from the human parasitic liver fluke Opisthorchis viverrini, known as <i>Ov</i>-GRN-1, induces angiogenesis and accelerates wound repair. Recombinant <i>Ov</i>-GRN-1 production is complex and poses an obstacle for clinical development. To identify the bioactive region(s) of <i>Ov</i>-GRN-1, four truncated N-terminal analogues were synthesized and characterized structurally using NMR spectroscopy. Peptides that contained only two native disulfide bonds lack the characteristic granulin β-hairpin structure. Remarkably, the introduction of a non-native disulfide bond was critical for formation of β-hairpin structure. Despite this structural difference, both two and three disulfide-bonded peptides drove proliferation of a human cholangiocyte cell line and demonstrated potent wound healing in mice. Peptides derived from <i>Ov</i>-GRN-1 are leads for novel wound healing therapeutics, as they are likely less immunogenic than the full-length protein and more convenient to produce