ProTX-I

M.W. 3987.5

C₁₇₁H₂₄₅N₅₃O₄₇S₆

Glu – Cys – Arg – Tyr – Trp – Leu – Gly – Gly – Cys – Ser – Ala – Gly – Gln – Thr – Cys – Cys – Lys – His – Leu – Val – Cys – Ser – Arg – Arg – His – Gly – Trp – Cys – Val – Trp – Asp – Gly – Thr – Phe – Ser

T-Type Ca2+ Channel / Na+ Channel / K+ Channel Blocker (Gating Modifier) ProTx-I was isolated from the venom of the tarantula thrixopelma pruriens and the primary structure was determined to consist of 35 amino acid residues with three intrachain disulfide bonds [Biochemistry 41, 14734 (2002)]. This peptidic ion channel blocker shows sequence similarity to hanatoxin and belongs to a member of the "inhibitor cystine knot" peptide family.Like other venomous toxins, ProTx-I exerts inhibitory activities for each ion channels: T-type Ca2+ channel [Cav3.1 (α1G), IC50 = 53 nM], Na + channel [Nav1.2, Nav1.5, Nav1.7 (IC50 = 51 nM), and Nav1.8 (IC50 = 27 nM)], K + channel [Kv2.1 (IC50 = 411 nM) and Kv1.3 (40% blocking at 730 nM)]. ProTx-I thus elicits multiple channel blocking activities with certain selectivity since K+ channel inhibitory activity is relatively weak. ProTx-I is one of the first high-affinity ligands to be identified that possess tetrodotoxin-resistant Na+ and T-type Ca2+ channel blocking activity. This peptide should prove useful for elucidating the gating mechanism of voltage-dependent ion channels.

Synthetic Product (disulfide bonds between Cys2– Cys16, Cys9– Cys21 and Cys15– Cys28 )