TAILIEUCHUNG - Báo cáo khoa học: Purification, characterization and biosynthesis of parabutoxin 3, a component of Parabuthus transvaalicus venom

A novel peptidyl inhibitor of voltage-gated K + channels, named parabutoxin 3 (PBTx3), has been puri®ed to homo-geneity from the venom ofParabuthus scorpion toxin contains 37 residues, has a mass of 4274 Da and displays 41% identity with charybdotoxin (ChTx, also called ). PBTx3 is the tenth member (called )ofsubfamily1ofK + channel-blocking pep-tidesknown thus far. | Eur. J. Biochem. 269 1854-1865 2002 FEBS 2002 doi Purification characterization and biosynthesis of parabutoxin 3 a component of Parabuthus transvaalicus venom Isabelle Huvs1 Karin Dvason2 Etienne Waelkens3 Fons Verdonck4. Johann van Zvl5. Johan du Plessis2 Gert J. Muller5 Jurg van der Walt2 Elke Clynen6 Liliane Schoofs6 and Jan Tytgat1 1Laboratory of Toxicology University of Leuven Leuven Belgium department of Physiology University of Potchefstroom Potchefstroom South Africa 3Laboratory of Biochemistry University of Leuven Leuven Belgium 4Interdisciplinary Research Centre University of Leuven Campus Kortrijk Kortrijk Belgium 5Department of Pharmacology University of Stellenbosch Tygerberg South Africa 6Laboratory for Developmental Physiology and Molecular Biology University of Leuven Belgium A novel peptidyl inhibitor of voltage-gated K channels named parabutoxin 3 PBTx3 has been purihed to homogeneity from the venom of Parabuthus transvaalicus. This scorpion toxin contains 37 residues has a mass of 4274 Da and displays 41 identity with charybdotoxin ChTx also called . PBTx3 is the tenth member called of subfamily 1 of K channel-blocking peptides known thus far. Electrophysiological experiments using Xenopus laevis oocytes indicate that PBTx3 is an inhibitor of Kv1 channels but has no detectable effects on Kir-type and ERG-type channels. The dissociation constants Kd for and channels are respectively 79 M 547 nM and 492 nM. A synthetic gene encoding a PBTx3 homologue was designed and expressed as a fusion protein with the maltose-binding protein MBP in Escherichia coli. The recombinant protein was purihed from the bacterial periplasm compartment using an amylose affinity resin column followed by a gel hltration purihcation step and cleavage by factor Xa fXa to release the recombinant toxin peptide rPBTx3 . After hnal purih-cation and refolding rPBTx3 was shown to be identical .

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