Reciprocal control of the conformational state of the sarcoplasmic reticulum calcium channel protein by polarization and depolarization in the transverse tubule

[摘要]

We attached the conformational probe methylcoumarin acetate (MCA) specifically to the junctional foot protein (JFP) moiety of triads, and monitored conformational changes in the JFP during polarization and depolarization of the T-tubule moiety. The MCA fluorescence decreased upon T-tubule polarization, and the fluorescence changes were blocked by preventing T-tubule polarization or by a nimodipine block of the T-tubule-to-sarcoplasmic reticulum communication. Depolarization of the T-tubule reversed the MCA fluorescence decrease which had been produced by T-tubule polarization. These results suggest that the conformational and functional states of the JFP are regulated by T-tubule polarization and depolarization in a reciprocal fashion.

[学科分类] 生物化学/生物物理

[关键词] Excitation-contraction coupling;Triad;Junctional foot protein;Conformational change;Transverse tubule;BAPTA;1;2-bis(o-aminophenoxy)ethane-N;N;N′;N′-tetraacetic;acid;DHPR;dihydropyridine receptor;E-C coupling;excitation-contraction coupling;HEPES;N-2-hydroxyethyl piperazine-N′-2-ethane sulfonic acid;JFP;junctional foot protein;MCA;methylcoumarin acetate;MES;2-(N-morpholino)ethanesulfonic acid;PI buffer;buffer solution containing proteolytic enzyme inhibitors;PMSF;phenylmethanesulfonyl fluoride;SAED;sulfosuccinimidyl 3-((2-(7-azido-4-methylcoumarin-3-acetamido) ethyl) dithio)propionate;SR;sarcoplasmic reticulum;T-tubule;transverse tubular system