title: Crystallization of the Ca2+-ATPase of sarcoplasmic reticulum by calcium and lanthanide ions.
abstract: 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.
authors.forename: L
authors.initials: L
authors.lastname: Dux
authors.forename: K A
authors.initials: KA
authors.lastname: Taylor
authors.forename: H P
authors.initials: HP
authors.lastname: Ting-Beall
authors.forename: A
authors.initials: A
authors.lastname: Martonosi
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases; D002857:Chromium / Q000494:pharmacology; D003460:Crystallization; D004305:Dose-Response Relationship, Drug; D005614:Freeze Fracturing; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000494:pharmacology; D008564:Membrane Potentials; D008674:Metals, Rare Earth / Q000494:pharmacology*; D008854:Microscopy, Electron; D011189:Potassium Chloride / Q000494:pharmacology; D011487:Protein Conformation; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*; D013696:Temperature; D014357:Trypsin
chemical_list: D008674:Metals, Rare Earth; D002857:Chromium; D011189:Potassium Chloride; D000255:Adenosine Triphosphate; D014357:Trypsin; D000252:Calcium-Transporting ATPases; D008274:Magnesium; D002118:Calcium