Structural studies of the K+ Channel Blocker Tc32,from the Scorpion Tityus cambridgei

• Main Authors: I-Che Huang, 黃一喆
• Other Authors: 吳世雄
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/62848192842695498510

碩士 === 國立臺灣大學 === 生化科學研究所 === 92 === Abstracts: Ion channels are involved in diverse biological processes and play essential roles in the physiology of all cells. An increasing number of human and animal diseases have been identified to relate with the defective function of ion channels. Scorpion venoms contain various polypeptides (channel blockers) that particularly affect the permeability of ion channels in cell membranes. Thus, understanding the structural basis of the specificity of scorpion toxins for these receptors could lead to the design of new ligands with controlled activity and potency for clinical applications. Tc32 is a 35 amino acids peptide from the venom of Brazilian scorpion, Tityus cambridgei, which exhibits blocking activity against Kv1.3 and Shaker B potassium channels with different Kd values and is classified as the first member of the new subfamily of ?KTx(?KTx18.1). Sequence homology analysis shows that the two key residues, Lys and Tyr at C-terminus previously confirmed essential for activity, are mutated in Tc32. We synthesized Tc32 with solid phase synthesis. After refolding and purification, two-dimensional NMR and Circular Dichrorism were applied to determine the feature of secondary structure and three-dimensional solution structure of Tc32. Based on the specific NOEs, 3 disulfide bonds were unambiguously identified (C7-C26, C12-C31, and C16-C33) that is the same as native Tc32 identified by enzyme digestion and mass analysis. Tc32 structure shows that it consists a flexible region at N-terminus, and a rigid secondary structural scaffold with an?helix and a double-stranded antiparallel βsheet adopted by several other scorpion toxins. Although the rigid parts of the structure in Tc32 are similar with other scorpion toxins, the sequence alignment indicated that Tc32 might recognize the potassium channel using different residues. Comparing the structure of Tc32 and other scorpion toxins, structural and functional implications will be discussed