Crystallization of the Ca2+-ATPase of Sarcoplasmic Reticulum by Calcium and Lanthanide Ions

Two-dimensional crystalline arrays of Ca2+-ATPase molecules develop in sarcoplasmic reticulum vesicles exposed to Ca2+ or lanthanide ions. The Ca2+- or lanthanide-induced crystals are presumed to represent the E1 conformation of the Ca2+-ATPase, and their crystal form is clearly different from the earlier described E2 crystals induced by Na3VO4 in the presence of ethylene glycol bis(beta aminoethyl ether)-N,N,N',N'-tetraacetic acid (Taylor, K. A., Dux, L., and Martonosi, A. (1984) J. Mol. Biol. 174, 193-204). Analysis of the crystalline arrays by negative staining or freeze-fracture electron microscopy reveals obliquely oriented rows of particles corresponding to individual Ca2+-ATPase molecules. Computer analysis of the negatively stained lanthanide-induced crystalline Ca2+-ATPase arrays shows that the molecules are arranged in a P1 lattice. The pear-shaped profiles of Ca2+-ATPase molecules seen in projection in the density maps are similar to those seen in vanadate-induced crystals. The space group and unit cell dimensions of the E1 crystals are consistent with Ca2+-ATPase monomers as structural units, while the vanadate-induced E2 crystals form by lateral aggregation of chains of Ca2+-ATPase dimers. The transition between the E1 and E2 conformations may involve a shift in the monomer-oligomer equilibrium of the Ca2+-ATPase. The formation of E1 crystals by PrCl3 is promoted by inside negative membrane potential, presumably through stabilization of the E1 conformation of the enzyme. Cleavage of the Ca2+-ATPase by trypsin into two major fragments (A and B) did not interfere with the Ca2+- or the Pr3+-induced crystallization

Animal electricity, Ca2+ and muscle contraction. A brief history of muscle research

This brief review attempts to summarize some of the major phases of muscle research from Leeuwenhoek's description of sarcomeres in 1674, through Galvani's observation of "animal electricity" in 1791, to the discovery of Ca2+ as the key messenger in the coupling of nerve excitation to muscle contraction. The emerging molecular mechanism of the contraction process is one of the great achievements of biology, reflecting the intimate links between physics, chemistry and the life Sciences in the solution of biological problems

The network of calcium regulation in muscle.

In this review the molecular characteristics and reaction mechanisms of different Ca2+ transport systems associated with various membranes in muscle cells will be summarized. The following topics will be discussed in detail: a brief history of early observations concerning maintenance and regulation of cellular Ca2+ homeostasis, characterization of the Ca2+ pumps residing in plasma membranes and sarco(endo)plasmic reticulum, mitochondrial Ca2+ transport, Ca2+-binding proteins, coordinated expression of Ca2+ transport systems, a general background of muscle excitation-contraction coupling with emphasis to the calcium release channels of plasma membrane and sarcoplasmic reticulum, the structure and function of dihydropyridine and ryanodine receptors of skeletal and cardiac muscles, and finally their disposition in various types of muscles

The structure of the Ca2+-ATPase of sarcoplasmic reticulum.

In this article the morphology of sarcoplasmic reticulum, classification of Ca2+-ATPase (SERCA) isoenzymes presented in this membrane system, as well as their topology will be reviewed. The focus is on the structure and interactions of Ca2+-ATPase determined by electron and X-ray crystallography, lamellar X-ray and neutron diffraction analysis of the profile structure of Ca2+-ATPase in sarcoplasmic reticulum multilayers. In addition, targeting of the Ca2+-ATPase to the sarcoplasmic reticulum is discussed