Why Does the Inner-Helix Mutation A413C Double the Stoichiometry of Kv1.3 Channel Block by Emopamil but Not by Verapamil?

Rossokhin, A.; Dreker, T.; Grissmer, S.; Zhorov, B.S.

Авторы: Rossokhin A., Dreker T., Grissmer S., Zhorov B.S.
Журнал: Molecular Pharmacology
Том: 79
Номер: 4
Год издания: 2011
Издательство: American Society for Pharmacology and Experimental Therapeutics
Местоположение издательства: United States
Первая страница: 681
Последняя страница: 691
DOI: 10.1124/mol.110.068031
Аннотация: hKv1.3 channels in lymphocytes are targets for the chemotherapy treatment of autoimmune diseases. Phenylalkylamines block Kv1.3 channels by poorly understood mechanisms. In the inactivation-reduced mutant H399T, the second mutation A413C in S6 substantially decreases the potency of phenylalkylamines with a para-methoxy group at the phenylethylamine end, whereas potency of phenylalkylamines lacking this group is less affected. Intriguingly, completely demethoxylated emopamil blocks mutant H399T/A413C with a 2:1 stoichiometry. Here, we generated a triple mutant, H399T/C412A/A413C, and found that its emopamil-binding properties are similar to those of the double mutant. These data rule out disulfide bonding Cys412-Cys413, which would substantially deform the inner helix, suggest a clash of Cys413 with the para-methoxy group, and provide a distance constraint to dock phenylalkylamines in a Kv1.2-based homology model. Monte Carlo minimizations predict that the verapamil ammonium group donates an H-bond to the backbone carbonyl of Thr391 at the P-loop turn, the pentanenitrilephenyl moiety occludes the pore, whereas the phenylethylamine meta- and para-methoxy substituents approach, respectively, the side chains of Met390 and Ala413. In the double-mutant model, the Cys413 side chains accept H-bonds from two emopamil molecules whose phenyl rings fit in the hydrophobic intersubunit interfaces, whereas the pentanenitrilephenyl moieties occlude the pore. Because these interfaces are unattractive for a methoxylated phenyl ring, the ammonium group of respective phenylalkylamines cannot approach the Cys413 side chain and binds at the focus of P-helices, whereas the para-methoxy group clashes with Cys413. Our study proposes an atomistic mechanism of Kv1.3 block by phenylalkylamines and highlights the intra- and intersubunit interfaces as ligand binding loci.
Добавил в систему: Россохин Алексей Владимирович

	ИСТИНА	Войти в систему Регистрация
	ИСТИНА ЦЭМИ РАН
	Главная Поиск Статистика О проекте Помощь

ИСТИНА

ИСТИНА ЦЭМИ РАН

Why Does the Inner-Helix Mutation A413C Double the Stoichiometry of Kv1.3 Channel Block by Emopamil but Not by Verapamil?статья

Прикрепленные файлы