Photochemical localization of the semotiadil binding region within the cardiac Ca²⁺ channel α1 subunit. Comparison with the skeletal muscle counterpart

Abstract

We have previously identified the binding region of a new Ca 2+ antagonist semotiadil in the skeletal muscle Ca 2+

Photochemical Identification of the Binding Region for (S)-Semotiadil on Sodium Channels: Comparison with That for (R)-Semotiadil on Skeletal Muscle Calcium Channel

“…Here we show the results that identify photochemically the binding region of (S)-semotiadil in brain and cardiac Na + channels and compare it with that for (R)-semotiadil in L-type Ca 2+ channels we reported previously. 6,7 We also show and discuss the apparent enantioselectivity between (S)-and (R)-semotiadil for Na + -and Ca 2+ -channel, respectively, by comparative photolabeling. of the α-subunit.…”

“…Photoaffinity labeling is a powerful method to determine the ligand binding sites within the primary structures of target macromolecules. 5 Among wide applications of this technique, we previously identified the binding site of (R)-semotiadil in the sketetal muscle 6 and cardiac 7 L-type Ca 2+ channels as the region containing segment IVS6 using photoactivatable analog of (R)-semitiadil. We also compared the (R)-semotiadil binding site with those for well-known Ca 2+ antagonists, 1,4-dihydropyridines (DHP), phenylalkylamines (PAA), and benzothiazepines (BTZ), since the binding sites of Ca 2+ antagonists have been identified by photoaffinity labeling and site-directed mutagenesis.…”

Efficient identification of photolabelled amino acid residues by combining immunoaffinity purification with MS: revealing the semotiadil-binding site and its relevance to binding sites for myristates in domain III of human serum albumin

“…Several reports describe the application of this method to locate successfully the site of action of drugs or toxins in ion channels (see [5][6][7][8] for examples) at subpicomolar levels. The method, however, requires preparation of a large number of antibodies to efficiently identify only a limited number of labelled fragments.…”

“…, an azidophenyl derivative of semotiadil [7,8]. It has also been reported that semotiadil binds strongly to human serum albumin (HSA) in serum [22].…”

Efficient identification of photolabelled amino acid residues by combining immunoaffinity purification with MS: revealing the semotiadil-binding site and its relevance to binding sites for myristates in domain III of human serum albumin

“…radioactive photolabelled fragments. Several reports describe the application of this method to locate successfully the site of action of drugs or toxins in ion channels (see [5][6][7][8] for examples) at subpicomolar levels. The method, however, requires preparation of a large number of antibodies to efficiently identify only a limited number of labelled fragments.…”