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Query: UNIPROT:P06889 (Mol)
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The mitochondrial inner membrane contains specific binding sites for dihydropyridine (DHP) Ca2+ antagonists that are associated with an inner mitochondrial membrane anion channel (IMAC) [Mol. Pharmacol. 38:362-369 (1990)]. As in particulate preparations, binding of the DHP (+/-)-[3H]nitrendipine [( 3H]NTR) to partially purified mitochondrial DHP receptors strongly depended on a variety of cations and inorganic as well as organic anions. Monovalent anions saturably stimulated [3H]NTR binding with a potency rank order of I- greater than Br- greater than Cl- greater than F-. The potency rank order for monovalent cations was Cs+ greater than Rb+ greater than Li+ greater than K+ greater than Na+. [3H]NTR binding stimulation potency of the cations strikingly depended on their charge density, with EC50 values being 125 mM for K+, 5 mM for Ca2+, and 41 microM for La3+. This selectivity order clearly differed from one predicted on the basis of a simple surface charge-screening effect of the cations. In general, allosteric ion effects were due to changes in [3H]NTR affinity for the partially purified mitochondrial DHP receptor. SCN- and NO3-, known permeators of the IMAC [J. Biol. Chem. 262:15085-15093 (1987)], stimulated [3H]NTR binding with EC50 values of 26 mM and 96 mM, respectively. The IMAC permeators butylmalonate2- and 1,2,3-benzenetricarboxylate3- were ineffective when given alone but dose-dependently inhibited 500 mM NaCl-stimulated [3H]NTR binding, as did PO4(1.5-) and SO4(2-). Gluconate-, which was reported not to permeate the IMAC, qualitatively behaved as a partial agonist with respect to Cl-. Glucuronate- was without effect on [3H]NTR binding to the partially purified mitochondrial DHP receptor. These results point to the existence of rather large ion-binding domains. The cation-binding site was estimated to have a minimum diameter of 0.67 nm. The anion-binding domain could accommodate either spherical ligands with diameters of up to 0.6 nm or molecules with a flat backbone with dimensions of approximately 0.9 nm x 0.7 nm x 0.3 nm.
Mol Pharmacol 1992 Jan
PMID:Ion dependence of the partially purified mitochondrial dihydropyridine Ca2+ antagonist receptor. 131 Jan 45

Genetic transformation of cereals by direct DNA delivery via microprojectile bombardment has become an established procedure in recent years. But the derivation of functional transgenic plants, especially in wheat, is still problematic, mainly due to low efficiency of DNA delivery and the reduced regeneration capability of microprojectile-bombarded tissue. We focussed on these two aspects and found that the regeneration of scutellar calli of wheat can be rendered highly efficient and considerably accelerated by a liquid culture phase in screen rafts. We also found that the expression of a reporter gene following DNA delivery by microprojectile can be improved by maintaining the scutellar calli in 0.25 M mannitol before and after bombardment, by bombardment in the presence of silver thiosulfate and Ca(NO3)2 (rather than CaCl2) and by the elimination of spermidine from the DNA/microprojectile mixture. A protocol that includes all these features leads to several-fold higher transient expression of the reporter gene than have previously published procedures.
Mol Gen Genet 1992 Nov
PMID:Improvement of plant regeneration and GUS expression in scutellar wheat calli by optimization of culture conditions and DNA-microprojectile delivery procedures. 146 2

Cadmium speciation of the intestinal compartment of the earthworm species, Lumbricus terrestris, has been investigated using polyacrylamide gel electrophoresis under non-denaturing conditions. Worms exposed to Cd(NO3)2 supplemented soils have been studied and compared to control samples. Prior to electrophoresis, the worm intestines were removed and dissected. Proteins in the crude intestinal extracts were separated using polyacrylamide gel electrophoresis. The cadmium distribution in the proteins has also been described. In a second set of experiments, cadmium bound to proteins was first isotopically exchanged with labelled cadmium (109Cd) and then cadmium speciation was performed using gel electrophoresis. Autoradiography of this gel shows an intense band in the contaminated sample whereas this band was absent in the control sample. These results show that one type of major protein has a strong affinity for cadmium in the worm intestinal extract. This type of protein had a migration close of that of rabbit liver metallothionein used for comparison.
Mol Cell Biochem 1990 Sep 21
PMID:Cadmium speciation studies in the intestine of Lumbricus terrestris by electrophoresis of metal proteins complexes. 228 Jul 62

The stimulatory effects of two thiol (SH) group oxidants, methylmethane thiosulfonate (MMTS) and diazene dicarboxylic acid bis [N,N-dimethylamide] (diamide), on the kinetics of ouabain-resistant (OR) K:Cl [co]-transport in low K (LK) sheep red blood cells were compared with the effects of alkylating agents, notably N-ethylmaleimide (NEM). At low concentrations, both MMTS and diamide stimulated K:Cl [co]-transport, and with a latency period, as measured by OR zero-trans K efflux and OR uptake of external Rb, Rbo, as K congener in Cl and NO3 media. At high concentrations the effect of diamide saturated, and that of MMTS disappeared. The stimulatory effect of MMTS was partially reversed by the reducing agent dithiothreitol (DTT) known to fully restore the diamide-activated K flux (Lauf, J. Memb. Biol. 101:179-188, 1988). In diamide preequilibrated LK sheep red cells, the Km of K:Cl [co]-transport for external Cl, Clo, was 84.3 mM, and 18.7 mM for Rbo, with nearly identical Vmax values around 4 mmol Rb/L cells x h for K (Rb) fluxes in Cl and after correction for the small Cl-independent component. Zero net K (Rb) flux existed at Kc (cell K)/Rbo concentration ratios, [K]c/[Rb]c, of 0.8 i.e. when the electrochemical driving forces across the membrane were about equal. The measured K efflux/Rb influx ratios were almost twice those predicted from [K]c/[Rb]o and the Cl equilibrium potential suggesting that the diamide-stimulated K (Rb) flux may occur through non-diffusional, carrier-mediated transport.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Biochem
PMID:Kinetic comparison of ouabain-resistant K:Cl fluxes (K:Cl [Co]-transport) stimulated in sheep erythrocytes by membrane thiol oxidation and alkylation. 318 22

Rat thymocytes were exposed in vitro to the corticosteroid dexamethasone, 10 nM, for 10 min, or to oleic acid, 500 nM for 2 min. This results in cytolysis after 6 hr, if incubation is continued. Instead, the cells were centrifuged, the supernatant fluid decanted, and the cells subjected to osmotic shock in 1.5 mM MgCl2. The naked nuclei were incubated at 37 degrees C and examined by light and electron microscopy. Nuclear edema was evident early, and most nuclei showed damage with variation in shape and size and distinct folds, which was maximal by 1-2 hr as a result of these treatments. This was true also if nuclei were incubated in MgF2 or Mg(NO3)2 but not in MgBr2, MgI2, MgSO4 or Mg-citrate. Spleen lymphocyte nuclei showed similar damage but only after incubation with 20 microM oleic acid, and not at all with corticosteroids. The effects of both steroid and fatty acid, even at greatly increased concentrations, were inhibited by tri-n-butyl tin chloride, 10 microM, and by 4-4'-diisothiocyanostilbene-2,2'-disulfonic acid, sodium salt, 10 microM, both of which block chloride ion transport. It is concluded that the cytolytic effects of both corticosteroids and free fatty acids involve influx of chloride ion resulting in nuclear edema, which subsequently leads to fragmentation of chromatin, karyorrhexis and, ultimately, cytolysis.
Mol Cell Biochem 1984 Sep
PMID:Role of anions in the lymphocytolytic action of corticosteroids and fatty acids. 649 16

The DNA helix-coil transition in nonbuffer solutions of Fe(NO3)3 was studied. Calculation of the ionic equilibrium indicated that in these solutions iron exists in the form of mono-, bi- or trivalent hydroxide, the formation of which decreases pH. A component of the DNA thermal stability variation associated with DNA binding to iron ions was calculated. An increase in the iron contents produces an increase in the melting range which was determined by a rise in the melting end temperature when binding the ions with phosphates and a drop in the melting beginning temperature when binding to DNA bases. A main contribution to the former effect is made by [Fe2(OH)3]3+ ions and to the latter effect by [FeOH]2+ ions. The constants of ion binding are higher for bases than for phosphates. Differential UV spectra of native and denatured DNA due to iron ions were measured. Calculations of conformation and coordination components of these spectra show that G-C pairs are one of the possible sites of iron ion binding with DNA.
Mol Biol (Mosk)
PMID:[Binding of ions of trivalent iron with DNA]. 662 27

The wild-type heterocystous and nitrogen-fixing (Het+Nif+) N. muscorum and its non-heterocystous non-nitrogen-fixing (Het-Nif-) mutant strain both fail to grow in different inorganic nitrogen media containing 1 mM methylamine hydrochloride (MA). Mutants of the Het+Nif+ and Het-Nif- parents resistant to growth inhibition by 5 mM MA and thus designated as MAR strains were isolated with a frequency of 2.5(+/- 2.4) x 10(6). A MAR strain of the Het+Nif+ and a MAR strain of the Het-Nif- parent were characterized for growth, heterocyst formation and acetylene reducing activity in the presence and absence of methylamine in N2 medium. The Het+Nif+ MAR strain grows better in MA containing than in MA-free N2 medium, and all cultures grown with MA are found to lack both acetylene reducing activity and heterocyst. The Het-Nif-MAR strain shows good growth in MA-containing N2 medium but no growth in MA-free N2 medium. Furthermore, both the Het+Nif+MAR and Het-Nif-MAR strains show better growth in the presence than in the absence of MA in NO3- and HN4+ media. These results appear to suggest that the MAR phenotype in N. muscorum is due to the metabolic utilization of the ammonium analog as a nitrogen source.
Mol Gen Genet 1981
PMID:Isolation and preliminary characterization of mutants of the cyanobacterium Nostoc muscorum resistant to growth inhibition by methylamine. 679 49

The effects of ions on the interaction of lac repressor protein and operator DNA have been studied by the membrane filter technique. The equilibrium association constant was determined as a function of monovalent and divalent cation concentrations, anions, and pH. The binding of repressor and operator is extremely sensitive to the ionic environment. The dependence of the observed equilibrium constant on salt concentration is analyzed according to the binding theory of Record et al. [Record, M. T., Jr., Lohman, T. M., & deHaseth, P. L. (1976) J. Mol. Biol. 107, 145]. The number of ionic interactions in repressor--operator complex is deduced from the slopes of the linear log-log plots. About 11 ionic interactions are formed between repressor and DNA phosphates at pH 7.4 and about 9 ionic interactions at pH 8.0, in reasonable agreement with previous estimates. A favorable nonelectrostatic binding free energy of about 9-12 kcal/mol is estimated from the extrapolated equilibrium constants at the 1 M standard state. The values are in good accord with recent results for the salt-independent binding of repressor core and operator DNA. The effects of pH on the repressor--operator interaction are small, and probably result from titration of functional groups in the DNA-binding site of the protein. For monovalent salts, the equilibrium constant is slightly dependent on cation type and highly dependent on anion type. At constant salt concentration, the equilibrium constant decreases about 10000-fold in the order CH3CO2- greater than or equal to F- greater than Cl- greater than Br- greater than NO3- greater than SCN- greater than I-. The wide range of accessible equilibrium constants provides a useful tool for in vitro studies of the repressor--operator interaction.
 ...
PMID:Ion effects on the lac repressor--operator equilibrium. 727 80

Ionic fluxes in sea urchin sperm plasma membrane regulate cell motility and the acrosome reaction (AR). Although cationic channels mediate some of the ionic movements, little is known about anion channels in these cells. The fusion of sperm plasma membranes into lipid bilayers allowed identification of a 150 pS anion channel. This anion channel was enriched from detergent-solubilized sperm plasma membranes using a wheat germ agglutinin Sepharose column. Vesicles formed from this preparation were fused into black lipid membranes (BLM), yielding single channel anion-selective activity with the properties of those found in the sperm membranes. The following anion selectivity sequence was found: NO3- > CNS- > Br- > Cl-. This anion channel has a high open probability at the holding potentials tested, it is partially blocked by 4,4'-diisothiocyano-2,2'-stilbendisulfonic acid (DIDS), and it often displays substates. The sperm AR was also inhibited by DIDS.
Mol Reprod Dev 1993 Oct
PMID:Anion channels in the sea urchin sperm plasma membrane. 750 23

Products of inducible nitric oxide synthase (iNOS) are known to be involved in lung injury following intrapulmonary deposition of immunoglobulin G immune complexes (IgG-ICx). In the current studies rat alveolar macrophages stimulated in vitro with murine interferon gamma (IFN-gamma), tumor necrosis factor alpha, interleukin 1 alpha, (IL-1 alpha), lipopolysaccharide (LPS), or IgG-ICx immunostained for iNOS and produced nitrite/nitrate- (NO2-/NO3-) in a dose- and time-dependent manner requiring availability of L-arginine. Under the same conditions, IL-4 and IL-10 reduced NO2-/NO3- generation. Type II alveolar epithelial cells, which were obtained from normal rat lungs and stimulated in vitro with IgG-ICx, LPS, or IFN-gamma, also immunostained for iNOS and generated NO2-/NO3-. Special techniques of bronchoalveolar lavage (BAL) were used to retrieve alveolar macrophages and type II alveolar epithelial cells. Under these conditions, intrapulmonary deposition of LPS yielded BAL fluids containing increased amounts of NO2-/NO3- and macrophages that spontaneously released NO2-/NO3- and stained for iNOS. After intrapulmonary deposition of IgG both macrophages as well as type II cells (retrieved by BAL) spontaneously produced NO2-/NO3- and both cell types immunostained for iNOS (approximately 20% of all type II cells and 35% of all alveolar macrophages). Using dual fluorescence staining for cell identification, frozen sections of lung tissue after IgG immune complex deposition revealed iNOS in both alveolar macrophages and type II cells. Finally, in the immune complex model of alveolitis, the appearance of iNOS in macrophages as well as macrophage production in vitro of NO2-/NO3- was dependent on the in vivo availability of tumor necrosis factor alpha, IL-1, and IFN-gamma. These studies suggest a dual cell source for nitric oxide in inflamed lungs and the requirements for iNOS of several cytokines.
Am J Respir Cell Mol Biol 1995 Jun
PMID:Lung sources and cytokine requirements for in vivo expression of inducible nitric oxide synthase. 753 74


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