Photolabeled sites with a tetrodotoxin derivative in the domain III and IV of the electroplax sodium channel

• Published in: Biochemical and biophysical research communications Vol. 184; no. 2; pp. 900 - 907
• Main Authors: Nakayama, Hitoshi, Hatanaka, Yasumaru, Yoshida, Eiichi, Oka, Kozo, Takanohashi, Mayumi, Amano, Yuuka, Kanaoka, Yuichi
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 30.04.1992; Elsevier
• Subjects: Amino Acid Sequence; Animals; Binding Sites; Biological and medical sciences; Cell physiology; channels; domains; Electric Organ - metabolism; Electrophoresis, Polyacrylamide Gel; Electrophorus; Endopeptidases; Fundamental and applied biological sciences. Psychology; Immune Sera; Membrane and intracellular transports; Molecular and cellular biology; Molecular Sequence Data; Peptide Fragments - isolation & purification; Peptides - chemical synthesis; Peptides - immunology; photoaffinity labelling; sodium; Sodium Channels - metabolism; tetrodotoxin; Tetrodotoxin - metabolism; Torpedo; ESP; TPCK; SDS; STX; TTX; PAGE; TTXenDTB; DFP; Vertebrata; Immunoprecipitation reaction; Sodium; Pisces; Ionic channel; Binding site; Photoaffinity labelling; Electrophorus electricus; Electroplax
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/0006-291X(92)90676-C

Forty three percent of the labeled sites, at least, in the electroplax sodium channel with a photoactivable tetrodotoxin derivative were identified by probing protease-digested labeled fragments with several sequence-directed antibodies. They are located in the loop between segments S5 and S6 of domain IV, as well as the region containing transmembrane segment S6 and adjacent extracellular and cytoplasmic sequences in domain III. No photolabeled fragments were detected in the corresponding region of domain I. These results suggest that C-11 of tetrodotoxin where the photoreactive moiety is attached orients to the region between S5 and S6 in domain III and IV. Probable orientation of the tetrodotoxin molecule in sodium channels is considered by taking together with the recent report of the site-directed mutagenesis.