Synthesis and structural analysis of mutant K+ channel blocker Tc32, from the Scorpion Tityus cambridgei
Date Issued
2006
Date
2006
Author(s)
Chang, Sho-Fine
DOI
en-US
Abstract
Tc32 is a K+ channel-blocking peptide purified from the venom of Amazonian scorpion Tityus cambridgei and composed of 35 amino acid residues (TGPQT- TCQAA-MCEAG-CKGLG-KSMES-CQGDT-CKCKA) cross linked with three disulfide bridges. Tc32 is classified as the first number of the subfamily of a-KTx (a-KTx 18.1) based on sequence comparison with other members in a-KTx. In electrophysiological experiment, it shows blocking activity against Shaker/Kv1.x type channel. The three-dimensional structure of Tc32 has been previously investigated by our laboratory, and the structural fold of Tc32, a disulfide-stabilized a/b scaffold, is very similar with other a-KTxs. In sequence alignment analysis, some important residues of Tc32 are different from those in other a-KTxs. This indicates the recognition or blocking mechanism of Tc32 may be different. The docking model of Tc32 with Kv1.3 channel suggests that Lys34 inserts into the selectivity filter and interacts with the backbone carbonyls of GYG-motif from each subunit of the channel. In addition, other residues, such as Gln4, Lys17, Leu19, and Lys32, may be also involved in the recognition or blocking function. Structural studies show that the 3D structure of Tc32 and K34A mutant are very similar and they all contain an a-helix (Ala9-Leu19) and a double strand anti-parallel b-sheet (Ser22-Gln27 and Thr30-Ala34). The conformation is hold by three intramolecular disulfide bridges (Cys7-Cys26, Cys12-Cys31, and Cys16-Cys33). On the basis of the side-chain distribution and the potential surface plot, we suppose that side-chain effect should possess a greater impact on the blocking activity. Further bioassay of Tc32 as well as its mutants may reenforce our assumption.
Subjects
毒蠍
核磁共振
蠍毒
鉀離子通道抑制胜肽
NMR
Scorpion toxin
Tc32
K34A
Tityus cambridgei
Type
other
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