Assignment of the three disulfide bonds in ShK toxin: A potent potassium channel inhibitor from the sea anemoneStichodactyla helianthus
✍ Scribed by Jan Pohl; Frantisek Hubalek; Michael E. Byrnes; Kurt R. Nielsen; Amina Woods; Michael W. Pennington
- Publisher
- Springer Netherlands
- Year
- 1995
- Tongue
- English
- Weight
- 422 KB
- Volume
- 1
- Category
- Article
- ISSN
- 1573-3149
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✦ Synopsis
ShK toxin, a 35-residue peptide isolated from the Caribbean sea anemone Stichodactyla helianthus, is a potent inhibitor of the Kv1.3 potassium channel in lymphocytes. The natural toxin contains three disulfide bonds. The disulfide pairings of the synthetic ShK toxin were elucidated as a prerequisite for studies on its structure-function relationships. The toxin was fragmented at pH 6.5 using either thermolysin or a mixture of trypsin and chymotrypsin followed by thermolysin. The fragments were isolated by RP-HPLC and were identified by sequence analysis and MALDI-TOF mass spectrometry. The three disulfides were unambiguously identified in either proteolytic digest: Cys 3 to Cys 35, Cys ~2 to Cys 28 and Cys 17 to Cys 32. The CysLCys 35 disulfide, linking the aminoand carboxyl-termini, defines the characteristic cyclic structure of the molecule. A similar disulfide pairing motif is found in the snake venom-derived potassium channel blocker dendrotoxin and the mammalian antibiotic peptide defensins.