The role of the sites for ATP of the Ca2+-ATPase from human red cell membranes during Ca2+-phosphatase activity

1. In the presence of ATP, the Ca²⁺ pump of human red cell membranes catalyzes the hydrolysis of $\text{p-}\text{nitrophenyl}$ phosphate. The requirement for ATP of the Ca²⁺-$\text{p-}\text{nitrophenylphosphatase}$ activity was studied in relation to the two classes of site for ATP that are apparent during Ca²⁺ -ATPase activity. 2. (a) The $\text{K}{}_{0.5}$ for ATP as activator of the Ca²⁺ -$\text{p-}\text{nitrophenylphosphatase}$ extrapolated at 0 mM PNPP is equal to the $\text{K}{}_{\mathrm{<mtext>m</mtext>}}$ of the Ca²⁺ -ATPase. (b) PNPP competes with ATP and its effectiveness is the same regardless the nucleotide acts as the substrate of the Ca²⁺ -ATPase or as activator of the Ca²⁺ -$\text{p-}\text{nitrophenylphosphatase}$. 3. PNPP at the high-affinity site does not substitute for ATP as activator of the Ca²⁺ -$\text{p-}\text{nitrophenylphosphatase}$. 4. At ATP concentrations that almost saturate the high-affinity site, Ca²⁺ -$\text{p-}\text{nitrophenylphosphatase}$ activity increases as a function of PNPP along an S-shaped curve, while Ca²⁺ -ATPase activity is partially inhibited along a curve of the same shape and apparent affinity. The fraction of Ca²⁺ -ATPase activity which is inhibited by PNPP is that which results from occupation of the low-affinity site by ATP. 5. Activation of the Ca²⁺ -ATPase by ATP at the low-affinity site is associated with inhibition of the Ca²⁺ -$\text{p-}\text{nitrophenylphosphatase}$ activity. Both phenomena take place with the same apparent affinity and along curves of the same shape. 6. Experimental results suggest that: (a) the Ca²⁺ -$\text{p-}\text{nitrophenylphosphatase}$ activity depends on ATP at the high-affinity site; (b) PNPP is hydrolyzed at the low-affinity site; (c) Ca²⁺ -ATPase activity at the high-affinity size persists during Ca²⁺ -$\text{p-}\text{nitrophenylphosphatase}$ activity.     

Concerning the specificity of heme oxygenase: the enzymatic oxidation of synthetic hemins.

Hemin XIII $\text{4}\text{～}$, hemin III $\text{5}\text{～}$, and iron $\text{1,4-di(β-hydroxyethyl)porphyrin}\text{6}\text{～}$ were enzymatically oxidized by a microsomal heme oxygenase preparation from rat liver. These are all better substrates of the oxygenase than the natural substrate, hemin IX $\text{1}\text{～}$. The enzymatic oxidation was selective for the α-methine bridge and in every case only the α-biliverdins were obtained. The latter were readily reduced by biliverdin reductase to the corresponding α-bilirubins. The absence of isomers in addition to the α-bilirubins was established by preparing the derived azopigments and by using [α-¹⁴C]$\text{6}\text{～}$ and [α-¹⁴C]$\text{4}\text{～}$ as substrates. The chemical oxidation of $\text{4}\text{～}$, $\text{5}\text{～}$, and $\text{6}\text{～}$ gave the expected mixture of biliverdins. It is concluded that heme oxygenase is not specific for hemin IX. On the other hand, the enzyme is highly selective for the α-methine bridge, defined as the methine opposed to that flanked by the 6,7-propionic acid residues.     

Interaction between the nitrate respiratory system of Escherichia coli K12 and the nitrogen fixation genes of Klebsiella pneumoniae.

Hybrids were constructed between $\text{E. coli}$ K12 $\text{chl}$^? mutants defective in nitrate respiration and an F′ plasmid carrying nitrogen fixation genes from $\text{K. pneumoniae}$. Examination of these hybrids showed that expression of $\text{nif}$_Kp⁺ genes does not require a functional nitrate respiratory system, but that nitrate reductase and nitrogenase do share some Mo-processing functions. For nitrate repression of nitrogenase activity, reduction of nitrate to nitrite is not necessary, but the Mo-X cofactor encoded by $\text{chl}$ genes is essential. Nitrate probably inhibits nitrogen fixation by affecting the membrane relationship of the nitrate and fumarate reduction systems such that the membrane cannot be energized for nitrogenase activity.     

Behavioral comparisons of the stereoisomers of tetrahydrocannabinols

The potencies of (?)-$\text{trans}$-Δ⁹-THC, (+)-$\text{trans}$-Δ⁹-THC, (+)-$\text{cis}$-Δ⁹-THC, (?)-$\text{trans}$-Δ⁸-THC and (+)-$\text{trans}$-Δ⁸-THC were compared in several different species. (?)-$\text{trans}$-Δ⁹-THC was 100 times more potent than (+)-$\text{trans}$-Δ⁹-THC in depressing schedule-controlled responding in monkeys. The (+)-$\text{trans}$ isomers were less effective than their corresponding (?)-$\text{trans}$ isomers in the dog static-ataxia test, but potency ratios could not be determined due to a lack of dose-responsiveness of the (+)-$\text{trans}$ isomers. However, it appeared that their potency differed by at least ten fold. The potency of (+)-$\text{cis}$-Δ⁹-THC in the dog static-ataxia test was comparable to that of (+)-$\text{trans}$-Δ⁹-THC. The hypothermia in mice produced by the (?) isomers of $\text{trans}$-Δ⁹-THC and $\text{trans}$-Δ⁸-THC were 9.1 and 30.4 times greater than that produced by their respective (+)-isomers. Also, the potency ratio of the (+)- and (?)-$\text{trans}$-Δ⁹-THC was 5.6 as measured by depression of spontaneous activity in mice. The magnitude of the potency ratios of the THC stereo-isomers is dependent upon the species and the pharmacological test used.     

The phosphorylation of troponin B by phosphorylase b kinase in skeletal muscle of mice carrying the phosphorylase b kinase deficiency gene

In skeletal muscle of animals with the phosphorylase $\text{b}$ kinase deficiency gene there is < 1% of the normal activity to convert phosphorylase $\text{b}$ to $\text{a}$ in the presence of Ca⁺⁺, Mg⁺⁺, and ATP (1). Correspondingly, there is < 1% of the normal activity to phosphorylate phosphorylase $\text{b}$. Nevertheless, under the same conditions, these extracts catalyze the phosphorylation of troponin at a rate 57% of normal. Phosphorylase $\text{b}$ converting activity can be sedimented from skeletal muscle of control mice by centrifugation. This fraction isolated from I strain skeletal muscle extracts phosphorylates troponin at a rate 29–39% of the control. EGTA¹ (15 mM) inhibits troponin phosphorylation by 50–60% in this fraction from both strains. The EGTA inhibition is reversed by 15 mM Ca⁺⁺. Thus the phosphorylase $\text{b}$ kinase in skeletal muscle of animals with the phosphorylase $\text{b}$ kinase deficiency gene can phosphorylate troponin B, although it shows little or no activity with phosphorylase as a substrate. This observation is consistent with the normal muscle contractility of I strain animals.     

The separation of phage promoter from bacterial lac promoter for beta-galactosidase expression in transducing phage lambda plac5.

The replication defective transducing phage λp$\text{lac}\text{5}\text{O}\text{29}\text{P}$3 carries a portion of the $\text{E.}\text{coli}\text{lac}$ operon in the $\text{b}$2 region of the lambda phage. This $\text{lac}$ operon segment contains the $\text{lac}$ promoter, the $\text{lac}$ operator, and the β-galactosidase $\text{z}$ gene, but does not contain the $\text{lac}$ repressor $\text{i}$ gene. The $\text{z}$ gene can be expressed from both the inserted $\text{lac}$ promoter and the phage promoter. When $\text{E.}\text{coli}$ strain 594 ($\text{z}$^?, $\text{i}$⁺) or JC6256 (Δ$\text{lac}$) is infected by λp$\text{lac}\text{5}\text{O}\text{29}\text{P}$3 in the absence of additional cyclic AMP, β-galactosidase synthesis is shown to be expressed from the phage promoter. When 594 (λ⁺) or JC6256 (λ⁺) is infected by λp$\text{lac}\text{5}\text{O}\text{29}\text{P}$3 in the presence of additional cyclic AMP and IPTG, β-galactosidase synthesis is shown to be expressed from the inserted $\text{lac}$ promoter.The ability to separate the phage promoter from the inserted $\text{lac}$ promoter for β-galactosidase expression will simplify the interpretation whenever λp$\text{lac}$5 is used.     

Replacement of the B protein requirement of the E. coli quinolinate synthetase system by chemically-generated iminoaspartate

Two proteins (A and B) from $\text{Escherichia}\text{,}\text{coli}$ are required for $\text{in}\text{,}\text{vitro}$ synthesis of the NAD⁺ precursor, quinolinate, from L-aspartate and dihydroxyacetone phosphate. The requirement for B protein and L-aspartate in this system can be replaced by millimolar concentrations of oxaloacetate and ammonia if they are added together. This finding supports the concept that the B protein (L-aspartate oxidase) functions to form iminoaspartate which is condensed with dihydroxyacetone phosphate by the A protein to form quinolinate.     

Inhibition of surfactant release from isolated type II cells by compound 4880

Release of [³H]phosphatidylcholine from pulmonary Type II epithelial cells was stimulated by terbutaline, forskolin and cytochalasin D. Compound $\text{48}\text{80}$ inhibited both basal and agonist-stimulated release of [³H]PC. The IC₅₀ for inhibition by compound $\text{48}\text{80}$ was 1–2 μg/ml, and was similar for inhibition of both basal and stimulated release of [³H]phosphatidylcholine. Inhibitory effects of $\text{48}\text{80}$ were noted following a 1 h exposure to compound $\text{48}\text{80}$ and persisted up to 3 h. The inhibitory effect of compound $\text{48}\text{80}$ was entirely reversed by removing compound $\text{48}\text{80}$ from the external milieu. Compound $\text{48}\text{80}$ had no effect on cytosolic cyclic AMP levels or lactate dehydrogenase release. Inhibition of surfactant release produced by compound $\text{48}\text{80}$ was unaffected by changes in extracellular calcium concentrations. Compound $\text{48}\text{80}$ is a non-toxic inhibitor of phosphatidylcholine release from Type II epithelial cells.     

Analysis of the kinetics of electron transfer reactions of hemoglobin and myoglobin with inorganic complexes.

The kinetics of methemoglobin reduction by Fe(EDTA)^2? have been studied and found to follow a second order rate law with k = 29.0 $\text{M}$^?1 s^?1 [25°C, μ = 0.2 $\text{M}$, pH 7.0 (phosphate)], $\text{ΔH}{}^3\text{= 5.5 ± 0.7 kcal/mol}$, and $\text{ΔS}{}^2\text{= ?33 ± 2 e.u.}$. The electrostatics-corrected self-exchange rate constant (k₁₁^corr) for hemoglobin based on the Fe(EDTA)^2? cross-reaction is 2.79×10^?3$\text{M}$^?1 s^?1. This rate constant is compared with others reported for a water-soluble iron porphyrin and calculated from published data for the reactions of myoglobin and hemoglobin with Fe(EDTA)^2? and Fe(CDTA)^2?/?. The k₁₁^corr values for these systems range over ten orders of magnitude with heme ? myoglobin > hemoglobin.     

Double dependence of organic acid active transport in proximal tubules of surviving frog kidney on sodium ions I. Influence of sodium ions in bath medium on the uptake and run out of fluorescein and uranin

With the aid of direct microfluorimetric determination of marker organic anions (fluorescein and uranin) accumulated in the proximal tubules the influence of Na⁺ in the bath medium on the active transport of these anions was studied. Kinetic analysis of the rate dependence of organic acid active transport into tubules on their concentration in the bath medium with a constant Na⁺ concentration permitted to define values of apparent $\text{K}{}_{\mathrm{<mtext>m</mtext>}}$ and $\text{V}$ for uranin and fluorescein transport in the medium with different Na⁺ content. It was shown that a decrease of Na⁺ concentration in the medium increases $\text{K}{}_{\mathrm{<mtext>m</mtext>}}$ and lowers the $\text{V/K}{}_{\mathrm{<mtext>m</mtext>}}$ ratio with uncharged $\text{V}$. By varying the Na⁺ concentration in the medium with a constant concentration of the marker anion the and values for fluorescein and uranin transport were determined. A value for fluorescein in twice as much that for uranin. The $\text{1/K}{}_{\mathrm{<mtext>m</mtext>}}$ value for uranin transport is a linear function of Na⁺ concentration, while for fluorescein transport it is a quadratic one. Therefore it is concluded that two Na⁺ from the medium participate in active transfer of one fluorescein anion whereas only one Na⁺ from the medium is required for active transfer of one uranin anion. The run out of fluorescein from tubules preloaded with this acid is sharply reinforced by the Na⁺ omission from the medium. Thus, active transport of organic acids in proximal tubules of frog kidney is Na⁺-dependent, and Na⁺ from the medium is likely to participate directly in formation of a transport complex. When Na⁺ is absent in the medium a carrier fulfils a facilitated diffusion only.     

Identification of opiate receptor binding in intact animals.

After intravenous administration of ³H-naloxone to rats, particulate bound radioactivity accumulated in the brain is selectively associated with opiate receptor binding sites, providing a means of labeling the opiate receptor $\text{in vivo}$. The regional distribution of ³H-naloxone bound $\text{in vivo}$ closely parallels regional differences in opiate receptor binding $\text{in vitro}$ with highest levels in the corpus striatum, negligible receptor-associated binding in the cerebellum and intermediate levels in other regions. ³H-Naloxone binding $\text{in vivo}$ is saturable with the same total number of binding sites determined $\text{in vivo}$ as by $\text{in vitro}$ procedures. Nalorphine is markedly more potent than morphine in inhibiting ³H-naloxone binding $\text{in vivo}$ and non-opiates are ineffective. The half-life for dissociation of ³H-naloxone bound to particles $\text{in vivo}$ is the same as its dissociation rate after binding occurs $\text{in vitro}$, and sodium stabilizes ³H-naloxone bound $\text{in vivo}$ from initial rapid dissociation as predicted from the known properties of the opiate receptor $\text{in vitro}$.     

Preparation of metaphase chromatin of Physarumpolycephalum without the loss of repressed RNA synthesis

A novel method for the preparation of intact chromatin from the slime mold $\text{Physarum}\text{polycephalum>}$ which retains the $\text{in}\text{vivo}$ property of RNA synthesis is described. Preparations from G₂-cells were highly active, while those from metaphase-cells were inactive. The plasmodial cells were disrupted by gentle homogenization on a polyethylene sieve in a neutral isotonic sucrose medium containing Mg⁺⁺, deoxycholate and EGTA, a Ca⁺⁺-chelating agent. The nuclei were lysed in a hypotonic buffer without use of EDTA and chromatin was precipitated by centrifugation after addition of Mg⁺⁺.     

Synthesis of quinolinate from D-aspartate in the mammalian liver-Escherichia coli quinolinate synthetase system.

Two proteins (A and B) from $\text{Escherichia coli}$ are required for the synthesis of the NAD precursor quinolinate from aspartate and dihydroxyacetone phosphate. Mammalian liver contains a FAD linked protein which replaces $\text{E. coli}$ B protein for quinolinate synthesis. D-aspartic acid but not L-aspartic acid is a substrate for quinolinic acid synthesis in a system composed of the B protein replacing activity of mammalian liver and $\text{E. coli}$ A protein. In contrast the $\text{E. coli}$ B protein-$\text{E. coli}$ A protein quinolinate synthetase system requires L-aspartic acid as substrate. The previous report that L-aspartate was a substrate in the liver-$\text{E. coli}$ system was due to contamination of commercially available [¹⁴C]L-aspartate with [¹⁴C]D-aspartate. These and other observations suggest that liver B protein is D-aspartate oxidase and $\text{E. coli}$ B protein is L-aspartate oxidase.     

Occurrence of cis-7-tetradecenoic acid in the envelope phospholipids of Escherichia coli K12

We have isolated a tetradecenoic acid from $\text{E}\text{.}\text{coli}$ and have identified this new acid as $\text{cis}$-7-tetradecenoic by its ¹³C nuclear magnetic resonance spectrum. This identification was confirmed by conventional structural studies. The acid is a component of the phospholipids of $\text{E}\text{.}\text{coli}$ and comprises about 15% of the total phospholipid unsaturated fatty acid.     

Isolation of an acyl-CoA carboxylase from the tapeworm spirometra mansonoides

An acyl-CoA carboxylase, which catalyzes the carboxylation of acetylpropionyl-, and butyryl-CoA, has been isolated from the tapeworm $\text{Spirometra}\text{mansonoides}$. The enzyme has an absolute requirement for ATP, Mg²⁺, and HCO₃${}^{\mathrm{?}}$ and, in addition, requires K⁺ for full catalytic activity. The enzyme has been purified 50-fold by a combination of calcium phosphate gel adsorption, ion-exchange column chromatography, and gel filtration. In its substrate specificity, K⁺ requirement, molecular size, and antigenic behavior, the tapeworm enzyme is similar to the acyl-CoA carboxylase of another helminth— the free-living nematode $\text{Turbatrix}\text{aceti}$.     

The incision and strand rejoining step in the excision repair of 5,6-dihydroxy-dihydrothymine by crude E. coli extracts

Strand resealing in the $\text{in}$$\text{vitro}$ excision repair of 5,6-dihydroxy-dihydrothymine in osmium tetroxide oxidized polyd(A-T) by crude $\text{E.}$$\text{coli}$ extracts is accomplished by polynucleotide ligase. Osmium tetroxide oxidized polyd(A-T)_serves as a chemically well defined model substrate containing damage of the kind introduced into DNA by ionizing radiation. In the first incision step of excision repair approximately one endonucleolytic nick is introduced into the polymer by extracts of $\text{E.}$$\text{coli}$ endoI^? and $\text{E.}$$\text{coli}$ endoI^?$\text{uvr}$A6^? per ring damaged thymine residue removed.     

Stimulation by interferon of induction of differentiation of human promyelocytic leukemia cells

F₁-ATPase was isolated from yeast $\text{S.}\text{cerevisiae}$. The constituent subunits 1 and 2 were purified by gel permeation chromatography, and their amino acid compositions determined. Both subunits have a similar composition except for $\text{1}\text{2}$ cystine, methionine, leucine, histidine, and tryptophan. When F₁ is treated for three hours with 5′-p-[³H]fluorosulfonylbenzoyl adenosine in dimethylsulfoxide, 90% of the activity is lost. Disc gel electrophoresis of the modified complex showed that over 90% of the label was associated with subunit 2. A labelled peptide from a $\text{S.}\text{aureus}$ digest of subunit 2 was isolated and sequenced. It had the following amino acid sequence: His-Try¹-Asp-Val-Ala-Ser-Lys-Val-Gln-Glu, whereby Tyr¹ is the modified amino acid residue. This sequence shows homology to other sequences obtained from maize, beef heart, and $\text{E.}\text{coli}$ F₁-ATPases.     

Peptide chain initiation with chemically formylated Met-tRNAs from E. coli and yeast

Chemically formylated Met-tRNA_m^Met and Met-tRNA_f^Met species from $\text{E.}$$\text{coli}$ and yeast were tested for their capacity to serve as chain-initiators in a cell-free system from $\text{E.}$$\text{coli}$. In the presence of R 17 mRNA, initiation factors and $\text{E.}$$\text{coli}$ ribosomes, all four Met-tRNAs could form functional initiation complexes as measured by ribosomal binding kinetics, fMet-puromycin formation and synthesis of a dipeptide fMet-Ala. Unformylated Met-tRNA_f^Met from $\text{E.}$$\text{coli}$ displayed significantly less activity as a peptide chain-initiator than the formylated Met-tRNA_m^Met species from $\text{E.}$$\text{coli}$ and yeast. Although the latter tRNAs were less effective initiators than the “physiological” initiator tRNAs, the data seem to indicate that a blocked α-amino group represents the major token of identification by which Met-tRNA is admitted to function in $\text{E.}$$\text{coli}$ peptide chain initiation.     

A Cl−/HCO3−-ATPase in the gils of Carassius Auratus. Its inhibition by thiocyanate

An ATPase is demonstrated in plasma membrane fractions of goldfish gills. This enzyme is stimulated by Cl^? and HCO₃^?, inhibited by SCN^?.Biochemical characterization shows that HCO₃^? stimulation ($\text{K}{}_{\mathrm{<mtext>m</mtext>}}\text{= 2.5}\text{mequiv./l}$) is specifically inhibited in a competitive fashion by SCN^? ($\text{K}{}_{\mathrm{<mtext>i</mtext>}}\text{= 0.25}\text{mequiv./l}$). The residual Mg²⁺-dependent activity is weakly is weakly affected by SCN^?.In the microsomal fraction chloride stimulation of the enzyme occurs in the presence of HCO₃^? ($\text{K}{}_{\mathrm{<mtext>m</mtext>}}\text{for chloride = 1 mequiv./l}$); no stimulation is observed in the absence of HCO₃^?. Thiocyanate exhibits a mixed type of inhibition ($\text{K}{}_{\mathrm{<mtext>i</mtext>}}\text{= 0.06}\text{mequiv./l}$) towards the Cl^? stimulation of the enzyme.Bicarbonate-dependent ATPase from the mitochondrial fraction is stimulated by Cl^?, but this enzyme has a relatively weak affinity for this substrate ($\text{K}{}_{\mathrm{<mtext>m</mtext>}}\text{= 14}\text{mequiv./l}$).