Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Ca-ATPase activity of membranous scallop sarcoplasmic reticulum was found to be unstable when the Ca(2+)-binding sites on the Ca-ATPase were unoccupied. The decay in activity could be slowed or halted by inclusion in the preincubation medium of Na+, K+, nucleotides, ethylene glycol, or high concentrations of choline chloride. Stabilization of the Ca(2+)-free Ca-ATPase by Na+ and K+ showed a markedly different concentration dependence to that seen with activation of the Ca(2+)-activated ATPase activity by the two ions. Examination in the electron microscope of scallop membranes negatively stained in the presence of EGTA under conditions where the enzyme had been stabilized against lack of Ca2+ always showed vesicles containing dimer ribbon structures, whereas unstabilized membranes did not show dimer ribbons. There was an association between the effectiveness of a medium in stabilizing the enzyme in the presence of EGTA and the extent and quality of the dimer arrays seen in the microscope. Comparison of the range of Ca2+ concentration over which the Ca(2+)-binding sites on the scallop Ca-ATPase titrated with the range over which the dimer ribbon structural state was lost indicated that the Ca(2+)-binding sites on the Ca-ATPase must be empty for dimer ribbon formation to occur. Previous studies (Franzini-Armstrong, C., Ferguson, D. G., Castellani, L., and Kenney, L. J. (1987) Ann. N. Y. Acad. Sci. 483, 44-56) have found that the Ca-ATPase molecules in scallop adductor muscle freeze-fractured after fixation under relaxing conditions are arranged in dimer ribbons. Thus, the association of stabilization of the Ca(2+)-free Ca-ATPase with the presence of dimer ribbons implies that one function of the dimer state may be to stabilize the scallop enzyme in situ, when the Ca2+ concentration in the sarcoplasm is low and the muscle is relaxed.
 ...
PMID:A possible role for the dimer ribbon state of scallop sarcoplasmic reticulum. Dimmer ribbons are associated with stabilization of the Ca(2+)-free Ca-ATPase. 183 65

Fragmented sarcoplasmic reticulum prepared from the cross-striated adductor muscle of the deep sea scallop (Placopecten magellanicus) was phosphorylated with inorganic phosphate to the E2P (ADP-insensitive) form. Negative staining of these preparations showed that the Ca-ATPase was organized into a quasi-crystalline array, which differed from the 'dimer ribbon' structure previously reported for the membrane under relaxing conditions (Castellani & Hardwicke, J. cell. Biol. 97 (1983) 557-61; Castellani et al., J. molec. Biol. 185 (1985) 579-94). In this new form there was only a single Ca-ATPase per unit cell. Dephosphorylation of the E2P membranes and incubation with substrate or substrate analogues in the absence of Ca2+ caused the 'dimer ribbon' structure to appear. These results imply that rotation of at least half of the Ca-ATPase subunits in the scallop sarcoplasmic reticulum may occur about an axis perpendicular to the plane of the membrane on conversion from the E2P state to the state corresponding to that existing in the relaxed muscle.
 ...
PMID:Effect of phosphorylation on scallop sarcoplasmic reticulum. 252 48

In membranous scallop sarcoplasmic reticulum, the alkali metal cations Na+ and K+ and nucleotide together promote dimer formation by the Ca(2+)-free Ca-ATPase and stabilize the enzyme activity [Kalabokis, V. N., Bozzola, J. J., Castellani, L., & Hardwicke, P. M. D. (1991) J. Biol. Chem. 266, 22044-22050]. The dependence of stabilization of the Ca(2+)-free membranous scallop Ca-ATPase on Na+ concentration does not show saturation and may involve several superimposed effects. In order to assess the contribution of dimer toward stabilization, i.e., determine the relative importance of intra- and intermolecular effects on stabilization, the influence of varying Na+ concentration and nucleotide on the decay of enzyme activity of the Ca(2+)-free detergent-solubilized Ca-ATPase was studied. Loss of enzyme activity on removal of Ca2+ with EGTA was associated with loss of capacity for phosphorylation by ATP, a Ca(2+)-dependent function. Stabilization of the soluble Ca(2+)-free enzyme by Na+ showed major differences from that seen with the membranous enzyme. The extent of stabilization of the Ca(2+)-free soluble enzyme by Na+ showed clear saturation with increasing Na+ concentration. In contrast to the Ca(2+)-free membranous enzyme, which is inactivated at pH 7.0 with biphasic first-order kinetics, loss of enzymatic function by the solubilized Ca-ATPase at pH 6.92, 0 degrees C, followed monophasic first-order kinetics.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Effect of Na+ and nucleotide on the stability of solubilized Ca(2+)-free Ca-ATPase from scallop sarcoplasmic reticulum. 847 66

To examine the expressed gene profile during encystation of Acanthamoeba castellanii Castellani, we used differentially expressed gene (DGE) screening by RT-PCR with 20 sets of random primers. From this analysis, we found that approximately 16 genes showed upregulation during encystation. We chose 6 genes, which had relatively higher expression levels, for further investigation. Based on homology search in database, DEG2 showed 55% of similarity with xylose isomerase, DEG9 showed 37% of similarity with Na P-type ATPase, and DEG14 showed 77% of similarity with subtilisin-like serine proteinase. DEG3 and DEG26 were identified as hypothetical proteins and DEG25 exhibited no significant similarity to any known protein. Encystation of Acanthamoeba has been suggested to be a process to resist adverse environmental or nutritional conditions. Further characterization studies of these genes may provide us with more information on the encystation mechanism of Acanthamoeba.
 ...
PMID:Differentially expressed genes of Acanthamoeba castellanii during encystation. 1816 10