Structural insights into transmembrane helix S0 facilitated RyR1 channel gating by Ca2+/ATP

Figures

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  Fig. 1. The structure of RyR1(S0/5 mM[Ca2+]) and binding sites of S0. a The cryo-EM density map of S0/5 mM[Ca2+] shows an extra density, indicating an extra TM helix S0 with a small loop in lumen (dark green). Three RyR1 subunits (I, II, and III) are shown in the cutting section to allow a clear visualization of S0. The model of S0/5 mM[Ca2+] in S0 and luminal domain (red box in (a)) are illustrated in side-view (b), cytoplasmic view (c), and luminal view (d). e, f are enlarged regions from c (circle) and d (rectangle), respectively. I, II, III, and IV represent four subunits in the RyR1 tetramer. * indicates the mutagenesis in patients with a family history of congenital myopathy (CCD).

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  Fig. 2. Conformational transitions of the whole and TM domain of RyR1 in different structures. a Structural illustration of domain organization. b Conformational transitions of RyR1-sample 1 upon Ca2+ loading. Condition 1 (EGTA) is shown in gray; condition 2 (100 nM [Ca2+]) is colored by domains. HD1, green; NTD, yellow; Handle, cyan; central domain, purple; CTD, brown; pVSD, light blue; Pore, blue. c Conformational transitions from RyR1-sample 1 (condition 2, same color scheme as panel b) to RyR1-sample 2 in 100 nM Ca2+ (condition 3, brownish red). d Conformational transitions of RyR1-sample 1 from condition 2 (same color scheme as (b)) to condition 4 (20 μM[Ca2+]/ATP, pink). e Conformational transitions of RyR1-S0 from condition 4 (pink) to condition 5 (S0/20 μM[Ca2+]/ATP, teal). The insets show enlarged transmembrane structures and conformational change of the gate (I4937).

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  Fig. 3. Conformational transitions of the core region (central domain, VSC, CTD, pVSD, S4/S5 linker, and Pore) in the RyR1 functional state. a Structural illustration of domain organization: Central domain, purple; VSD, green; CTD, brown; pVSD, light blue; Pore, blue. b–f show the domain transitions from resting state (closed) (condition 1, gray) to activated state (open) (condition 3, colored). g–k show the domain transitions from the primed state (pre-open) (condition 4, pink) to the activated state (full open) (condition 5, colored).

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  Fig. 4. The modulation of RyR1 by Ca2+, ATP, Caffeine, and S0. Two opposite protomers are displayed with domains in a cartoon. a RyR1 in resting state without Ca2+ and the channel is closed. b In the presence of Ca2+, but S0 is decoupled to pVSD, RyR1 is in a primed state with a closed gate. c In the presence of Ca2+ and S0 is coupled to pVSD, RyR1 have two conformations (solid box), which are primed (gate is closed) and activated states (gate is open). d In the presence of Ca2+, ATP, and S0 is coupled to pVSD, RyR1 is in full open state. e In the presence of Ca2+ and ATP but S0 is decoupled to pVSD, RyR1 is in the primed state with a closed gate. f In the presence of Ca2+, ATP, and exogenous regulator (e.g., caffeine), RyR1 have two conformations (dashed box), which are primed (gate is closed) and open states (gate is open)24,36. g Schematic diagram of RyR1 channel gating mechanism. Ca2+/ATP/Caf regulates the channel through ɑ4/U motif-VSC-pVSD-S4/S5 linker-gate path (path I) and U motif/CTD-S6c path (path II), as indicated by the gray arrows. When S0 is coupled to pVSD, Ca2+/ATP regulates the channel through ɑ4/U motif-VSC-pVSD-S0-S4/S5 linker-gate path (path I) and path II. S0…