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Charybdotoxin and noxiustoxin, two homologous peptide inhibitors of the K + (Ca 2+ ) channel
Author(s) -
Valdivia Hector H.,
Smith Jeffrey S.,
Martin Brian M.,
Coronado Roberto,
Possani Lourival D.
Publication year - 1988
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(88)81439-x
Subject(s) - charybdotoxin , chemistry , peptide , amino acid , stereochemistry , cleavage (geology) , peptide sequence , cysteine , biochemistry , gene , enzyme , biology , paleontology , membrane potential , fracture (geology)
We show that noxiustoxin (NTX), like charybdotoxin (CTX) described by others, affects Ca 2+ ‐activated K + channels of skeletal muscle (K + (Ca 2+ ) channels). Chemical characterization of CTX shows that it is similar to NTX. Although the amino‐terminal amino acid of CTX is not readily available, the molecule was partially sequenced after CNBr cleavage. A decapeptide corresponding to the C‐terminal region of NTX shows 60% homology to that of CTX, maintaining the cysteine residues at the same positions. While CTX blocks the K + (Ca 2+ ) channels with a K d of 1–3 nM, for NTX it is approx. 450 nM. Both peptides can interact simultaneously with the same channel. NTX and CTX promise to be good tools for channel isolation.