title: Solid-phase synthesis of omega-agatoxin IVA, a P-type calcium channel blocker.
abstract: omega-Agatoxin IVA, isolated from the venom of funnel web spider Agelenopsis aperta, blocks potently and selectively P-type calcium channels. This toxin, composed of 48 amino acids and containing 8 cysteine residues, was synthesized by the solid-phase procedure. The Cys residues were protected by acetamidomethyl (Acm) groups which were removed by mercuric acetate. During treatment with mercuric acetate, a by-product was detected, involving modification of tryptophan residues by the Acm groups. This side reaction can be completely prevented by addition of an excess of tryptophan in the reaction medium during Acm deprotection. The resulting peptide was submitted to an oxidative refolding, in different conditions, in order to determine the most favourable protocol. After formation of the four disulphide bonds, the toxin was purified by successive preparative HPLC, on two different supports, and fully characterized by analytical HPLC, capillary electrophoresis, amino acid analysis, mass spectrometry and Edman degradation. It was found to block the P-type calcium channel with a similar biological potency as described for the natural product.
authors.affiliation: Faculté des Sciences Pharmaceutiques et Biologiques, CNRS URA 1309, France.
authors.forename: J
authors.initials: J
authors.lastname: Najib
authors.forename: T
authors.initials: T
authors.lastname: Letailleur
authors.forename: J C
authors.initials: JC
authors.lastname: Gesquière
authors.forename: A
authors.initials: A
authors.lastname: Tartar
mesh_terms: D000818:Animals; D001681:Biological Assay; D002121:Calcium Channel Blockers / Q000138:chemical synthesis* / Q000737:chemistry* / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D004220:Disulfides / Q000737:chemistry / Q000302:isolation & purification; D005563:Formic Acid Esters / Q000737:chemistry; D013058:Mass Spectrometry; D011689:Purkinje Cells / Q000187:drug effects; D051381:Rats; D013111:Spider Venoms / Q000138:chemical synthesis* / Q000737:chemistry* / Q000378:metabolism; D013112:Spiders; D020867:omega-Agatoxin IVA
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004220:Disulfides; D005563:Formic Acid Esters; D013111:Spider Venoms; D020867:omega-Agatoxin IVA; C000345:t-butyloxycarbonyl group