Assignment of the three disulfide bonds in ShK toxin: A potent potassium channel inhibitor from the sea anemone Stichodactyla helianthus |
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Authors: | Jan Pohl Frantisek Hubalek Michael E Byrnes Kurt R Nielsen Amina Woods and Michael W Pennington |
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Institution: | (1) Microchemical Facility, Emory University, Clifton Road N.E., 30322 Atlanta, GA, U.S.A.;(2) Bachem Bioscience Inc., 3700 Horizon Drive, 19406 King of Prussia, PA, U.S.A.;(3) Oncology Department, Johns Hopkins School of Medicine, 21205 Baltimore, MD, U.S.A. |
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Abstract: | Summary ShK toxin, a 35-residue peptide isolated from the Caribbean sea anemone Stichodactyla helianthus, is a potent inhibitor of the Kv 1.3 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: Cys3 to Cys35, Cys12 to Cys28 and Cys17 to Cys32. The Cys3-Cys35 disulfide, linking the amino- and 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. |
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Keywords: | Neurotoxin Disulfide bonds Potassium channel toxin Protein sequence |
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