Similarity of three-dimensional microcrystals of detergent-solubilized (Na+,K+)-ATPase from pig kidney and Ca(2+)-ATPase from skeletal muscle sarcoplasmic reticulum

Image analysis has been used to compare the projection structure of three-dimensional crystals of (Na+,K+)-ATPase from pig kidney and the Ca(2+)-ATPase from rabbit muscle sarcoplasmic reticulum. These crystals, formed from detergent-solubilized protein in the presence of 20% glycerol and at a low detergent to protein ratio, crystallize in nearly identical unit cells in the space group C2. Average cell dimensions for the Ca(2+)-ATPase were a = 166.8 +/- 4.5 A, b = 57.7 +/- 4.4 A, gamma = 90 degrees while those for the (Na+,K+)-ATPase were a = 166.2 +/- 3.8A, b = 54.25 +/- 3.5A, gamma = 90 degrees. Their projected structures at the resolution of 25-A resolution are indistinguishable. Thus, the (Na+,K+)-ATPase crystals appear to contain only the alpha chain of the alpha beta heterodimer found in native membranes. We conclude from this that the three-dimensional structure of the alpha chain of the (Na+,K+)-ATPase is very similar to that of the Ca(2+)-ATPase despite their relatively weak overall sequence homology.

Spontaneous rupture of the kidney: a report on 5 cases

Five cases of spontaneous rupture of the renal parenchyma are reported. Two patients had renal cell cancer, one sustained acute purulent pyelonephritis secondary to stone related ureteral obstruction, one suffered from aposthematous pyelonephritis without obstruction, while one had chronic pyelonephritis and a cortical cyst as probable predisposing factors. Aetiology and important points concerning diagnosis and therapy are discussed.

Further characterization of the 3-dimensional crystals of detergent-solubilized (Na+,K+)-ATPase from pig kidney

Multilamellar 3-dimensional (Type I) crystals of detergent-solubilized, purified (Na+, K+)-ATPase enzyme of pig kidney grow in media consisting of 0.1 M KCl, 0.1 M NaCl, 20 mM imidazole pH: 7.5 (20 degrees C), 5 mM MgCl2, 5 mM DTT, 3 mM ZNaN3, 0.025 TIU/ml Aprotinin, 2 micrograms/ml BHT and 20-40% glycerol, using nonionic detergents of C12E8 or BRIJ 36 for solubilization. The refined crystallization protocol: the use of media containing 20% glycerol, the low detergent: protein ratio and preincubation at subzero temperature at the initial phase of crystallization resulted in a remarkable increase of the yield and overall dimension of the crystals (up to 3-4 microns), while the stacking of the crystalline sheets was dramatically reduced. Biochemical and structural analysis of these crystals revealed further similarities between the 3-d crystals of the (Na+, K+)-ATPase and the Ca2+ ATPase of skeletal muscle-SR (Taylor and Varga, J. Biol. Chem., 269, 10107-10111, 1994). Computer image processing of the electron micrographs of stacked crystalline sheets of (Na+,K+)-ATPase molecules gave unit cell dimensions: a = 166.2 +/- 3.8 A, b = 54.2 +/- 3.5 A, with an included angle of 90 degrees C. Based on the close identity of the filtered images in projection and of other data, we concluded that the 3-dimensional crystals of the (Na+, K+)-ATPase contain only the alpha catalytic subunits.

3-dimensional (type I) microcrystals of detergent-solubilized (Na+, K+)-ATPase enzyme from pig kidney

3-dimensional crystalline arrays (Type I) of the ion transporting (Na+, K+)-ATPase enzyme from pig kidney develop in detergent-solubilized crude membrane-fragments or purified (Na+, K+)-ATPase preparations upon exposure to 0.1 M KCl and 0.1 M NaCl at pH 7.4 for several days at 2 degrees C in a crystallization medium that preserves the ATPase activity. Crystallization was obtained with non-ionic detergents; C12E8, C12E9, C12E10, and BRIJ 36 at a detergent: protein.ratio ranging from 1.8:1 to 4.4:1 in purified (Na+, K+)-ATPase preparations. High concentration of glycerol (40% v/v), Mg2+ ions and low temperature proved to be essential for crystallization and for protection of ATPase activity. Cross-linking of (Na+, K+)-ATPase crystals with glutaraldehyde protects the crystalline structure under conditions which otherwise disrupt the preformed crystals. The new crystals show close resemblance to the 3-dimensional crystals of the Ca(2+)-ATPase featuring the same structure of stacked lamellae. High-resolution electron microscopy of frozen-hydrated (Na+, K+)-ATPase samples is in progress to give unit cell dimensions and molecular packing of the new crystals.

Giant sarcoplasmic reticulum vesicles: a study of membrane morphogenesis

Rabbit sarcoplasmic reticulum vesicles were fused into giant proteoliposomes in a medium of 0.1 M KCl, 10 mM Tris-maleate, pH 7.0, 10 micrograms ml-1 antipain, 10 micrograms ml-1 leupeptin, 25 IU per ml Trasylol, 3 mM NaN3, 3.75% PEG 1500 and 3% DMSO by brief exposure to 37 degrees C, followed by incubation for 4 h at 25 degrees C. Approximately 5-10% of the sarcoplasmic reticulum elements underwent fusion, forming single-walled spherical vesicles of 1-25 microns diameter, in which the polarity of the native membrane was preserved. The Ca(2+)-stimulated ATPase activity remained essentially unchanged after fusion. On exposure to decavanadate in a Ca(2+)-free medium the spherical vesicles assumed a corrugated appearance with the formation of long ridges separated by deep furrows that eventually pinched off longitudinally and separated into numerous long crystalline tubules of uniform (approximately 0.1 microns) diameter. The vanadate-induced transformation of giant vesicles into tubules implies that the geometry of the sarcoplasmic reticulum membrane is determined by the conformation of the Ca(2+)-ATPase.

Immunological relatedness of the sarcoplasmic reticulum Ca(2+)-ATPase and the Na+,K(+)-ATPase

The effect of anti-ATPase antibodies with epitopes near Asp-351 (PR-8), Lys-515 (PR-11) and the ATP binding domain (D12) of the Ca(2+)-ATPase of sarcoplasmic reticulum (EC 3.6.1.38) was analyzed. The PR-8 and D12 antibodies reacted freely with the Ca(2+)-ATPase in the native membrane, indicating that their epitopes are exposed on the cytoplasmic surface. Both PR-8 and D12 interfered with the crystallization of the Ca(2+)-ATPase, suggesting that their binding sites are at interfaces between ATPase molecules. PR-11 had no effect on ATPase-ATPase interactions or on the ATPase activity of sarcoplasmic reticulum. The epitope of PR-11 is suggested to be the VIDRC sequence at residues 520-525, while that of D12 at residues 670-720 of the Ca(2+)-ATPase. The use of predictive algorithms of antigenicity for identification of potential antigenic determinants in the Ca(2+)-ATPase is analyzed.

Effects of solutes on the formation of crystalline sheets of the Ca(2+)-ATPase in detergent-solubilized sarcoplasmic reticulum

The Ca(2+)-ATPase crystals formed in detergent solubilized sarcoplasmic reticulum (SR) at 2 degrees C in a crystallization medium of 0.1 M KCl, 10 mM K-Mops (pH 6.0), 3 mM MgCl2, 3 mM NaN3, 5 mM DTT, 25 IU/ml Trasylol, 2 micrograms/ml 1,6-di-tert-butyl-p-cresol, 20% glycerol and 20 mM CaCl2 (J. Biol. Chem. 263, 5277 and 5287 (1988)) contain highly ordered sheets of ATPase molecules, that associate into large multilamellar stacks (greater than 100 layers). When the crystallization is performed in the same medium but in the presence of 40% glycerol at low temperature the stacking is reduced to 4-5 layers and the average diameter of the crystalline sheets is increased from less than 1 micron to 2-3 microns. Glycerol and low temperature presumably reduce stacking by interfering with the interactions between the hydrophilic headgroups of Ca(2+)-ATPase molecules in adjacent lamellae, while not affecting or promoting the ordering of ATPase molecules within the individual sheets. Electron diffraction patterns could be regularly obtained at 8 A and occasionally at 7 A resolution on crystals formed in 40% glycerol, either at 2 degrees C or at -70 degrees C. In the same media but in the absence of glycerol, polyethyleneglycol 1450, 3000 and 8000 (1-8%) induced the formation of ordered crystalline arrays containing 10-12 layers that were similar to those obtained in 40% glycerol. Replacement of 40% glycerol with 10-50% glucose or supplementation of the standard crystallization medium with polyethyleneglycol (PEG 3000 or 8000; 1, 2, 5 and 8%) had no beneficial effect on the order of crystalline arrays compared with media containing 40% glycerol.

Polarized infrared attenuated total reflectance spectroscopy of the Ca(2+)-ATPase of sarcoplasmic reticulum

The mean orientations of the transition dipole moments associated with vibrational modes of the proteins and phospholipids of sarcoplasmic reticulum were determined on dry and hydrated membrane multilayers deposited on germanium or zinc selenide crystals, using polarized infrared attenuated total reflectance spectroscopy (P-IR-ATR). For preservation of the enzymatic activity of the Ca(2+)-ATPase the films were prepared from solutions containing 0.05 M KCl, 5 mM imidazole (pH 7.4), 0.5 mM MgCl2, 1-10 mM trehalose and dithiothreitol. The anisotropy was highest in dry films containing congruent to 7.5 micrograms protein/cm2, and decreased with increasing membrane thickness or hydration. The dichroic ratio of the CH2 vibrations (2923 cm-1) of extracted sarcoplasmic reticulum phospholipids on Ge plate was 1.56, compared with a dichroic ratio of 1.68 obtained on dry films of whole sarcoplasmic reticulum. The dichroic ratios of the amide I band (1650 cm-1) of the Ca(2+)-ATPase in the Ca2-E1 state and in the EGTA and vanadate stabilized E2-V state were nearly identical (1.60 vs. 1.62). The dichroism of the amide I, amide II and lipid CH2 vibrations was not affected by changes in the concentration of KCl (25-100 mM) or Ca2+ (approximately equal to 10(-8)-10(-4) M) and by the addition of vanadate (1 mM) or Pi (5 mM) in a calcium-free medium containing 0.5 mM EGTA. The dichroic ratio of the C-C (1033 cm-1) or CO stretching band (1046 cm-1) of trehalose incorporated into SR films was 1.2 on Ge plate; this corresponds to a mean angle of approximately 70 degrees between the plane of the trehalose ring and the normal of the film plane, suggesting that the trehalose molecules are surprisingly well oriented in the polar headgroup region of the phospholipids. The orientation of the trehalose was not affected by the presence of Ca(2+)-ATPase.

Covalent labeling of the cytoplasmic or luminal domains of the sarcoplasmic reticulum Ca(2+)-ATPase with fluorescent azido dyes

Sarcoplasmic reticulum (SR) vesicles were incubated with azido derivatives of Cascade blue (ACB), Lucifer yellow (ALY), 2,7-naphthalene-disulfonic acid (ANDS), and fluorescein (AF) for 0.1-24 h at 2 degrees C. All four dyes gave intense reaction with the cytoplasmic domain of the Ca(2+)-ATPase on photoactivation after brief incubation. The penetration of the dyes into the luminal space of the SR was determined after centrifugation through Sephadex microcolumns to remove the external dye, followed by photolabeling and gel electrophoresis of the photolabeled proteins. The reaction of ACB and ANDS with the Ca(2+)-ATPase and with calsequestrin increased progressively during incubation up to 24 h indicating their slow accumulation in the luminal space, while ALY and AF did not show significant penetration into the vesicles. The distribution of the covalently attached ACB in the Ca(2+)-ATPase was tested by tryptic proteolysis after labeling exclusively from the outside (OS), from the inside (IS) or from both sides (BS). In all cases intense ACB fluorescence was seen in the A fragment with inhibition of ATPase activity. In the OS preparations the A1, while in IS the A2 fragment was more intensely labeled. There was no significant incorporation of ACB into the region of B fragment identified by FITC fluorescence. The crystallization of the Ca(2+)-ATPase by EGTA + decavanadate was completely inhibited in the BS samples after labeling either in the Ca2E1 or E2V conformation. There was no inhibition of crystallization in the OS preparations. In the IS preparations labeled in the Ca2E1 state the crystallization was impaired, while in the E2V state there was only slight disorganization of the crystals. The total amount of ACB photoincorporated into SR proteins after incubation for 24 h was 1.75 nmol/mg protein; 2/3 of this labeling occurred from the outside and 1/3 from the inside. Similar level of labeling was obtained in media that stabilize the E1 or the E2 conformation of the Ca(2+)-ATPase.

Differences in the susceptibility of various cation transport ATPases to vanadate-catalyzed photocleavage

Illumination of sarcoplasmic reticulum vesicles by ultraviolet light in the presence of 1 mM vanadate causes photocleavage of the Ca(2+)-ATPase into two fragments (Vegh et al. (1990) Biochim. Biophys. Acta 1023, 168-183). In the absence of Ca2+ the photocleavage occurs in the N-terminal half of the molecule near the phosphate acceptor Asp-351. In the presence of 2 mM Ca2+ the photocleavage shifts to the C-terminal half of the ATPase, near the FITC binding site (Lys-515). About half of the Ca(2+)-ATPase was cleaved rapidly, accompanied by nearly complete, irreversible loss of ATPase activity when illuminated in the presence of 2 mM CaCl2; further cleavage of the enzyme was slow and affected primarily the C-terminal fragment produced in the presence of Ca2+. Solubilization of the Ca(2+)-ATPase with C12E8 did not affect the site of photocleavage in either conformation. The vanadate-induced Ca(2+)-ATPase crystals were disrupted during photocleavage, while the binding of anti-ATPase antibodies directed against the phosphorylation site (PR-8) and against the FITC binding region (PR-11) was enhanced. The bovine kidney Na+,K(+)-ATPase was insensitive to photocleavage under conditions where about half the Ca(2+)-ATPase was fragmented. The slight cleavage of the pig gastric H+,K(+)-ATPase after prolonged illumination produced fragments that are distinct from the fragments of the Ca(2+)-ATPase.

Emerging views on the structure and dynamics of the Ca2(+)-ATPase in sarcoplasmic reticulum

The ATP-dependent Ca2+ transport in sarcoplasmic reticulum involves transitions between several structural states of the Ca2(+)-ATPase, that occur without major changes in the secondary structure. The rates of these transitions are modulated by the lipid environment and by interactions between ATPase molecules. Although the Ca2(+)-ATPase restricts the rotational mobility of a population of lipids, there is no evidence for specific interaction of the Ca2(+)-ATPase with phospholipids. Fluorescence polarization and energy transfer (FET) studies, using site specific fluorescent indicators, combined with crystallographic, immunological and chemical modification data, yielded a structural model of Ca2(+)-ATPase in which the binding sites of Ca2+ and ATP are tentatively identified. The temperature dependence of FET between fluorophores attached to different regions of the ATPase indicates the existence of 'rigid' and 'flexible' regions within the molecule characterized, by different degrees of thermally induced structural fluctuations.

Electron microscope observations on Ca2+-ATPase microcrystals in detergent-solubilized sarcoplasmic reticulum

Crystalline arrays of Ca2+-ATPase molecules develop in detergent-solubilized sarcoplasmic reticulum during incubation for several weeks at 2 degrees C under nitrogen in a medium of 0.1 M KCl, 10 mM K-3-(N-morpholino)propanesulfonate, pH 6.0, 3 mM MgCl2, 20 mM CaCl2, 20% glycerol, 3 mM NaN3, 5 mM dithiothreitol, 25 IU/ml Trasylol, 2 micrograms/ml 1,6-di-tert-butyl-p-cresol, 2 mg/ml protein, and 2-4 mg of detergent/mg of protein. Electron microscopy of sectioned, negatively stained, freeze-fractured, and frozen-hydrated Ca2+-ATPase crystals indicates that they consist of stacked lamellar arrays of Ca2+-ATPase molecules. Prominent periodicities of ATPase molecules within the lamellae arise from a centered rectangular lattice of dimensions 164 x 55.5 A. The association of lamellae into three-dimensional stacks is assumed to involve interactions between the exposed hydrophilic headgroups of ATPase molecules, that is promoted by glycerol and 20 mM Ca2+. Similar Ca2+-induced crystals were observed with purified or purified and delipidated Ca2+-ATPase preparations at lower detergent/protein ratios. Cross-linking of Ca2+-ATPase crystals with glutaraldehyde protects the structure against conditions such as low Ca2+, high pH, elevated temperature, SH group reagents, high concentration of detergents, and removal of phospholipids by extraction with organic solvents that disrupt unfixed preparations.

Effect of chemical modification on the crystallization of Ca2+-ATPase in sarcoplasmic reticulum

The influence of chemical modification on the morphology of crystalline ATPase aggregates was analyzed in sarcoplasmic reticulum (SR) vesicles. The Ca2+-ATPase forms monomer-type (P1) type crystals in the E1 and dimer-type (P2) crystals in the E2 conformation. The P1 type crystals are induced by Ca2+ or lanthanides; P2 type crystals are observed in Ca2+-free media in the presence of vanadate or inorganic phosphate. P1- and P2-type Ca2+-ATPase crystals do not coexist in significant amounts in native sarcoplasmic reticulum membrane. The crystallization of Ca2+-ATPase in the E2 conformation is inhibited by guanidino-group reagents (2,3-butanedione and phenylglyoxal), SH-group reagents, phospholipases C or A2, and detergents, together with inhibition of ATPase activity. Amino-group reagents (fluorescein 5'-isothiocyanate, pyridoxal phosphate and fluorescamine) inhibit ATPase activity but do not interfere with the crystallization of Ca2+-ATPase induced by vanadate. In fluorescamine-treated sarcoplasmic reticulum the vanadate-induced crystals contain significant P1-type regions in addition to the dominant P2 form.

Pressure effects on sarcoplasmic reticulum

The irreversible effects of pressure (1-2000 atm) upon the enzymatic activity and structure of the Ca2+-ATPase of sarcoplasmic reticulum were investigated. Sarcoplasmic reticulum vesicles suspended in a medium of 0.1 M KCl, 10 mM imidazole, pH 7.0, 5 mM MgCl2, and 0.5 mM EGTA irreversibly lose their Ca2+ transport and Ca2+-stimulated ATPase activities on exposure to pressures of 800-2000 atmospheres. The pressure-induced inactivation of Ca2+-ATPase is accompanied by inhibition of the formation of phosphorylated enzyme intermediate, an increase in the passive Ca2+ permeability of the membrane, and structural changes in the Ca2+-ATPase as shown by disruption of Ca2+-ATPase membrane crystals, increased susceptibility to tryptic digestion, unmasking of SH groups, and loss of the conformational responses to Ca2+ and vanadate. The sensitivity to pressure is influenced by enzyme conformation. Ca2+ or vanadate + EGTA protect the Ca2+-ATPase against pressure-induced inactivation, implying a greater stability of the enzyme in the E1 and E2 states than in the conformational equilibrium that prevails at low [Ca2+] in the absence of vanadate. Protection against pressure inactivation was also observed in the presence of sucrose, glycerol, ethylene glycol and 1 M KCl, suggesting that water density modifying groups significantly affect the stability of Ca2+-ATPase under pressure.

Competition between decavanadate and fluorescein isothiocyanate on the Ca2+-ATPase of sarcoplasmic reticulum

The binding of vanadate and fluorescein isothiocyanate to the Ca2+-transport ATPase of sarcoplasmic reticulum (EC 3.6.1.3) was analyzed. Monovanadate binds to the Ca2+-transport ATPase at a single high affinity site (site 1), that is presumably related to the binding site for inorganic orthophosphate, and to one of the two sites for decavanadate. Binding of vanadate to this site stabilizes the enzyme in the E2 conformation, with inhibition of ATPase activity and the formation of crystalline arrays of Ca2+-ATPase. Decavanadate also binds with high affinity to a second site on the Ca2+-ATPase (site 2), that is blocked by fluorescein isothiocyanate and may be part of the binding site for ATP. Crystallization of Ca2+-ATPase in sarcoplasmic reticulum, labeled with fluorescein isothiocyanate, by either monovanadate or decavanadate implies that occupation of site 1, but not of site 2, by vanadate is required for the conformational change of Ca2+-ATPase leading to the formation of crystalline arrays.

The binding of vanadium (V) oligoanions to sarcoplasmic reticulum

The binding of monovanadate and decavanadate anions to sarcoplasmic reticulum vesicles was measured by equilibrium sedimentation. The affinity of vanadate binding and the molar amount of vanadium (V) bound at equilibrium is much greater with decavanadate than with monovanadate. The binding data can be rationalized in terms of one binding site per ATPase molecule for monovanadate and two sites per ATPase for decavanadate. The Ca-ATPase crystals formed with monovanadate and with decavanadate are similar in appearance, but decavanadate is particularly effective in promoting the crystallization of Ca2+-ATPase at low V concentration (10-100 microM) in a Ca2+-free medium.

[Effect of chronic vitamin D deficiency on joint cartilage]

The effect of six-months rachitic diet on the articular cartilage of 12 white Whistar male rats has been studied using light, polarisation, and electronmicroscopes. On the basis of our observations radical changes could be noticed. The intracellular accumulation of glycogen and lipid and the necrosis of cells in the proof/inner/zone indicate the modifications of the cell's structure. The effect of permanent diet on the ground substance of articular cartilage was identified by irregular collagen fibers, and quantitative and qualitative changes of GAGs. On the basis of several author's argumentations it can be supposed that different illness/insufficiency of liver and kidney, and disturbance of resorption in human/can induce similar changes of articular cartilage which was produced by a long term rachitic diet. The cytological picture after long lasting rachitic diet is comparable with the arthrosis.

Quantitative Estimation of Fecal Coliforms in Fresh and Frozen Fishery Products by APHA and Modified A-1 Procedures

Fresh, frozen and breaded fish were analyzed for fecal coliforms by the modified A-1 (A-1 M) and APHA procedures. The A-1 M method produced significantly lower numbers of fecal coliforms. The lower values derived by the A-1 M procedure were attributed to the inhibiting effect of sample sediment on gas formation in fermentation tubes. By altering the A-1 M technique, estimates comparable to those produced by the presently used APHA method were obtained. Changes consisted of an increase in incubation time at 44.5°C and/or elevating gas vials in the culture tubes.

Alterations of the connective tissue in nude mice

The epiphyseal cartilage of nude mice was studied by light and electron microscopy. The resting and maturation zones become narrow and mineralization of the ground substance starts already in the zone of proliferation. Electron microscopy reveals signs of degeneration in the chondrocytes of this latter zone. An increased osteoclast activity can be observed in the metaphysis. The alterations may be due to a decrease in T-cell-mediated immunoreactivity of nude mice, as well as to an increased production of the osteoclast-activating factor, which might be attributed, among other things, to the B lymphocytes or macrophages.

The effect of experimental hypothyrosis on the fine structure of the epiphyseal cartilage of young rats

Authors studied the effect of hypothyrosis induced by thyro-parathyroidectomy and mercaptoimidazole treatment on the fine structure of the proximal epiphyseal cartilage of tibia in growing male rats. It has been established that the cell density of the epiphyseal cartilage decreases in the experimental hypothyrosis, about 30 to 50% of the chondrocytes display degenerative signs, whereas the Golgisystem seems to be well developed. The most characteristic alteration appear in the zones of proliferation and maturation of the epiphyseal cartilage. The endoplasmic reticulum (ER) and mitochondria show a considerable regression also in the chondrocytes displaying minimal or even no signs of degeneration. Elements indicating calcification were encountered more frequently in the cartilaginous matrix of the zones of maturation and calcification under the effect of mercaptoimidazole treatment as compared to the controls, whereas the matrix of the animals operated was poorer in minerals than the corresponding zones of the controls. This difference is attributed by the authors to the different levels of thyrocalcitonin in the two kinds of experiments.