Cylindrical Crystallization of Ca2+-ATPase and Its Potential Role in Sarcoplasmic Reticulum Dynamics

Figures

• 

  Figure 2. Typical images of the elongated SR vesicles isolated from scallop muscle, exhibiting crystalline dispositions and crystal-patch assembly of ATPase molecules in the presence of ATP. (a) A tightly elongated vesicle with an ATPase dimer array. (b) A tightly elongated vesicle with an ATPase monomer array. (c) A round vesicle with an ATPase crystal-patch assembly. (d) A cracked vesicle with an ATPase crystal-patch assembly. (a’–d’) Schematic illustrations corresponding to the four types of ATPase arrays in the vesicles shown in panels (a–d). Scale bars in (a–d): 100 nm (Reproduced from [65]).

• 

  Figure 1. Typical images of tightly elongated rabbit SR vesicles, observed in the presence of ATP. (a) Vesicle with an ATPase crystal array at 0.04 nanomolar (nM) Ca2+. (a’) clear tetramer units of the ATPase particles shown in (a) are marked with red circles. (b) Vesicles without ATPase crystal array at 0.2 micromolar (µM) Ca2+. The illustrations between (a’,b) show the atomic models (top and side views) of a rabbit ATPase monomer (PDB 1T5S) [72] in the E1 state with bound calcium, prepared with Jmol (https://launchpad.net/jmol). Scale bars in (a,a’,b): 100 nm (Reproduced from [63]).

• 

  Figure 3. Schematic representation of the dynamic movement models of the rabbit ATPase molecule(s) accompanying E1–E2 transition. (a) Intermolecular movement of the molecules on the cytoplasmic surface of the SR membrane. Open and hatched circles denote the two different types of molecules (Reproduced from Ref. [58]). (b) Intramolecular movement of the molecule inside and outside the SR membrane. Structural data were taken from PDB and PDBTM (E1, PDB ID: 1EUL [42]; E2, PDB ID: 1IWO [43], and the E1 and E2 ribbon models were prepared with Jmol.

• 

  Figure 4. Schematic representation of calcium dependencies of ATPase activity [83], striated muscle tension development [98] and ATPase disposition of scallop in the presence of ATP. The calcium dependence of tension development was examined using a caged calcium molecule and a chemically skinned fiber bundle of the striated adductor muscle, and the output of the tension transducer was recorded on a pen recorder and as a filtered signal on a Nicolet ‘Explorer’ digital oscilloscope [98].

• 

  Figure 5. A model linking calcium-dependent crystallization of ATPase to contraction of the scallop muscle cell (see Figure 12 in Ref. [65] for details).

• 

  Figure 6. Diagram of a cross-striated adductor muscle cell in the resting state of a scallop (Reproduced from [64].)