RELEASE OF NITROGENOUS SUBSTANCES BY BREWER'S YEAST. IV. ENERGETICS IN SHOCK EXCRETION OF AMINO ACIDS

Lewis, M. J. (University of California, Davis), and H. J. Phaff. Release of nitrogenous substances by brewer's yeast. IV. Energetics in shock excretion of amino acids. J. Bacteriol. 89:960-966. 1965.-When suitably grown yeast cells are suspended in a solution of fermentable sugar, amino acids from the internal pool are rapidly released from the cells, a phenomenon referred to as shock excretion. After approximately 2 to 3 hr, in the presence of excess sugar, the amino acids are almost completely reabsorbed. This observation has been further studied with particular reference to the energy-yielding reactions of the cell. It has been established that amino acid release increases more rapidly with a rise in incubation temperature than does fermentation rate. Amino acid release cannot be inhibited by the common uncouplers of adenosine triphosphate synthesis (azide, arsenate, or 2,4-dinitrophenol) at concentrations adequate to prevent reabsorption of amino acids-an energy-requiring event. Inhibitors which completely inhibit the dissimilation of glucose (such as iodoacetate and fluoride) or those preventing entry of glucose into the cell (uranyl acetate) are effective in preventing amino acid release. It was concluded that shock excretion of amino acids is independent of energy-yielding reactions, but may be the result of changes in the state of the cell contingent upon the continuous flow of a fermentable sugar across the cell membrane.

SODIUM EXTRUSION AND POTASSIUM UPTAKE IN GUINEA PIG KIDNEY CORTEX SLICES

Slices from the cortex corticis of the guinea pig kidney were immersed in a chilled solution without K and then reimmersed in warmer solutions. The Na and K concentrations and the membrane potential V_m were then studied as a function of the Na and K concentrations of the reimmersion fluid. It was found that Na is extruded from the cells against a large electrochemical potential gradient. Q₁₀ for net Na outflux was ∼2.5. At bath K concentrations larger than 8 mM the behavior of K was largely passive. At the outset of reimmersion (V_m > E_K) K influx seemed secondary to Na extrusion. Na extrusion would promote K entrance, being limited and requiring the presence of K in the bathing fluid. At bath K concentrations below 8 mM, K influx was up an electrochemical potential gradient. Thus a parallel active K uptake is apparent. Q₁₀ for net K influx was ∼2.0. Dinitrophenol inhibited net Na outflux and net K influx, Q₁₀ became <1.1 for both fluxes. The ratio between these fluxes varied. Thus at the outset of reimmersion the net Na outflux to net K influx ratio was >1. After 8 minutes it was <1.

CALCIUM ION ACCUMULATION AND VOLUME CHANGES OF ISOLATED LIVER MITOCHONDRIA. REVERSAL OF CALCIUM ION-INDUCED SWELLING

1. The excessive accumulation of Ca(2+) by mitochondria suspended in an iso-osmotic buffered potassium chloride medium containing oxidizable substrate and phosphate led to extensive swelling and release of accumulated Ca(2+) from the mitochondria. When the Ca(2+) was removed from the medium by chelation with ethylene glycol bis(aminoethyl)tetra-acetate, the swelling was reversed in a respiration-dependent contraction. The contracted mitochondria were shown to have regained some degree of respiratory control. 2. The respiration-dependent contraction could be supported by electron transport through a restricted portion of the respiratory chain, and by substrates donating electrons at different levels in the respiratory chain. 3. Respiratory inhibitors appropriate to the substrate present completely inhibited the contraction. Uncoupling agents, and the inhibitors oligomycin and atractyloside, were without effect. 4. When the reversal of swelling had been prevented by respiratory inhibitors, the addition of ATP induced a contraction of the mitochondria. In the absence of added chelating agent the contraction was very slow. The ATP-induced contraction was completely inhibited by oligomycin and atractyloside, was incomplete in the presence of uncoupling agents and was unaffected by respiratory inhibitors. 5. The relationship between the energy requirements of respiration-dependent contraction and the requirements of ion transport and other contractile systems are discussed.

THE ACCUMULATION OF CALCIUM IONS BY SARCOTUBULAR VESICLES

The accumulation of Ca(++) by microsomal (sarcotubular) preparations of rabbit skeletal muscle in the presence of oxalate, and the concurrent splitting of nucleoside triphosphate, displayed moderate nucleotide specificity in the sequence ATP > GTP, CTP, ITP > UTP > (ADP) > ATetraP for the former, ATP > (ADP) > ITP > GTP > CTP > UTP > ATetraP for the latter process. The "calcium pump" was weakly inhibited by caffeine, and was inhibited together with the ATPase by pyridoxalphosphate. Carnosine had no effect as such nor in the presence of pyridoxalphosphate except at high concentration; thiourea and p-chloromercuribenzoate were inhibiting while iodoacetate was inactive. Ca(++) accumulation and ATPase were inhibited by atabrine (not tested on ATPase), dinitrophenol, and amytal. High concentrations of oligomycin and rutamycin inhibited Ca(++) uptake while slightly stimulating ATPase. Antimycin A stimulated the Ca(++) uptake. These results are discussed in the light of their possible relation to partial reactions in oxidative phosphorylation. The Ca(++) uptake and relaxing factor activities did not behave identically throughout. This is in part ascribed to changes in reactivity of actomyosin in the relaxation test, in part to the participation of relaxing substances other than the calcium pump.

THE ROLE OF ADENOSINE TRIPHOSPHATE IN TRANSPORT REACTIONS

The evidence bearing on the participation of adenosine triphosphate (ATP) in transport reactions is reviewed. The connection may take the form of a strict quantitative relationship as observed in potassium uptake by red blood cells or as in amino acid uptake by slices of rat brain cortex. There may also be a qualitative relationship such as that observed in studies of amino acid uptake by Ehrlich ascites carcinoma cells. In other tissues (e.g. slices of the Ehrlich carcinoma) amino acid uptake may only have an uncertain relationship to the ATP content of the tissue. Some of the schemes which have been put forward to account for the involvement of ATP are discussed.

SODIUM FLUXES IN DESHEATHED FROG SCIATIC NERVE

Desheathed frog (R. pipiens) sciatic nerves were soaked in solutions that contained ouabain or NaN₃, in K-free solutions, or in K- and Ca-free solutions. Then, the nerves were allowed to recover in standard Ringer's solution. At various times during the soaking periods, some nerves were analyzed for Na and K, and estimates were made of the influx and efflux of Na²². While a nerve was soaking in any one of the experimental solutions, the Na²² influx was increased, the Na content was rising, and the K content was falling by an equivalent amount. The rate coefficient for Na²² efflux was reduced by about 25 per cent by 0.05 mM ouabain and by about 50 per cent by 5 mM NaN₃. Potassium-free solutions had little effect on the rate coefficient. It was concluded that the efflux of Na from frog nerve is dependent on the metabolism, but not on the external concentration of K. The equimolar exchange that is characteristic of the net movements of Na and K in frog nerve may not be due to the presence of a tightly coupled Na-K exchange pump, but may represent a constraint imposed by the requirement for electroneutrality.

INTERCONNECTION BETWEEN ACTIVE TRANSPORT AND CONTRACTURE IN UTERINE TISSUES

A study of the effects of several procedures known to interfere with active transport in rat, rabbit, and cat uterine muscle has revealed certain differences between muscles and between inhibitory procedures. Ouabain, fluoride, and sudden cooling caused an initial contracture followed by subsequent loss of contractility in circumstances in which they inhibit active transport. Removal of external potassium increased and subsequently decreased isometric contractions at 37 °C of rat and cat uterine segments, and in most of rat uterine horns caused contracture at 24 °C followed by relaxation and loss of contractility. The parallelism between the initial contracture and inhibition of active transport extends to the necessity for a concentration of 10−4 M to 10−3 M ouabain for initiation of both in rat uteri in contrast to the effectiveness of 10−7 M to 10−5 M in rabbit and cat uteri. The contracture induced by ouabain in rat uteri was potentiated by a decrease in external potassium and prevented by an increase. Removal of the glucose from the medium for 1 to 2 minutes potentiated both ouabain and potassium depletion contractures, but did not significantly increase potassium loss. Lower concentrations of NaF caused contracture in the absence of glucose. The contractures induced by NaF and by cold were obtained in uteri depolarized by K2SO4 Ringer solution and none were prevented by selective antagonists to acetylcholine, adrenaline, histamine, or serotonin. All the procedures producing contracture were ineffective in uteri depleted of calcium. All are known to interfere with the activity of the Mg- and Na + K-activated membrane ATPase believed to be involved in active transport. Therefore, it is proposed that inhibition of this enzyme in uteri causes contracture. In view of other work, this is presumed to occur by failure of active extrusion or failure of binding of calcium at the cell surface leading to a net calcium influx. The potentiation of contractures by removal of glucose occurs too rapidly to derive from glucose or glycogen depletion and is attributed to interaction between glucose transport and cation transport mechanisms.In contrast to ouabain, fluoride, potassium depletion, and cold, iodoacetate and dinitrophenol inhibit active transport and contractility in uterine muscle without causing an initial contracture. It is proposed that these substances act either by decreasing energy supply or by acting at a non-membrane site different from that at which substances causing contracture act. Cyanide was less effective as an inhibitor of either process, and oxidative metabolism is presumed not to be essential for energy supply in these tissues. In general, the loss of ability of uterine muscle to contract on chemical stimulation was directly related to the extent of potassium depletion. Both potassium depletion and loss of contractility were attributed to decreased energy supply.Ouabain in concentrations insufficient to cause contracture or potassium loss in rat uteri prevented rhythmic activity.

CYANIDE FORMATION BY CHROMOBACTERIUM VIOLACEUM

Michaels, Ruth (Columbia University, New York, N.Y.), and W. A. Corpe. Cyanide formation by Chromobacterium violaceum. J. Bacteriol. 89:106-112. 1965.-The formation of cyanide by a Chromobacterium violaceum strain was studied with growing cultures and with nonproliferating cells grown in complex and chemically defined media. Most of the cyanide was produced during the log-phase growth of the organism, and accumulated in the culture supernatant fluid. A synergistic effect of glycine and methionine on cyanide formation in a chemically defined medium was observed, and the amount of cyanide formed was found to be dependent on the concentrations of the two substances. Cyanide formation by nonproliferating cells was stimulated by preincubation with glycine and methionine. Cyanide formation by adapted cells in the presence of glycine and methionine was stimulated by succinate, malate, or fumarate, and depressed by azide and 2,4-dinitrophenol. Methionine could be replaced by betaine, dimethylglycine, and choline.

APPLICATION OF A LOCALIZED HEMOLYSIN REACTION FOR SPECIFIC DETECTION OF INDIVIDUAL ANTIBODY-FORMING CELLS

A technique is described which makes it possible to detect individual antibody-forming cells using a localized hemolysis reaction in a thickened culture medium containing sheep erythrocytes and guinea pig complement. This technique has the advantage over single cell isolation in that it is technically feasible to survey large populations in order to detect a very small active fraction. The cells can be observed continuously during the time of antibody release, and it appears that an estimate of the relative antibody-forming activity can be made from the size of the areas of lysis. Experiments with metabolic inhibitors indicate that active synthesis is occurring rather than release of preformed antibody. Some experiments on the detection of antibody other than anti-red cell antibodies are reported. This technique has been applied to a study of the induction period of the primary response of rabbits to sheep red blood cells. The results of this experiment are consistent with an induction period of 2 to 3 days during which there is no increase in the number of active cells in spleen and lymph node reflecting the lag in appearance of detectable serum antibody followed by an abrupt rise of 50- to 100-fold between the 3rd and 5th day. However, the present data are not sufficient to exclude various other mechanisms.

SULFATE TRANSPORT IN HUMAN RED CELLS: INHIBITION BY SOME UNCOUPLERS OF OXIDATIVE PHOSPHORYLATION

Release of inorganic sulfate from human erythrocytes is depressed in the presence of 2,4-dinitrophenol (5 x 10(-4)M) or dicumarol (5 x 10(-4)M). This effect cannot be readily attributed to uncoupling of phosphorylation from respiration, since the study was conducted with cells that metabolize principally by anaerobic means and since the effect was not influenced by iodoacetic acid. A more reasonable explanation may be that permeability of the erythrocyte membrane to anions may be reduced by these agents.

STUDIES ON ARTIFICIAL ANTIGENS. III. THE GENETIC CONTROL OF THE IMMUNE RESPONSE TO HAPTEN-POLY-L-LYSINE CONJUGATES IN GUINEA PIGS

The genetic transmission of the capacity to develop an immune response to hapten-polylysine conjugates was studied in guinea pigs. 82 per cent of the 22 offspring of 8 pairs of responder (guinea pigs which are capable of an immune response) parents were also responders, whereas, none of the 26 offspring of 9 pairs of non-responder parents were responders. None of 11 strain 13 guinea pigs and 100 per cent of 40 strain 2 guinea pigs were responders. These findings are consistent with the view that the capacity to respond immunologically to hapten-polylysine conjugates is genetically transmitted as a unigenic Mendelian dominant.

THE ISOLATION OF AMINO ACIDS FROM MIXTURES AS THEIR N-2,4-DINITROPHENYL DERIVATIVES, METHIONINE, LEUCINE, PHENYLALANINE, ORNITHINE, LYSINE AND TYROSINE

1. The separation of the dinitrophenyl derivatives of methionine, leucine (together with isoleucine), phenylalanine, ornithine, lysine and tyrosine from each other, and from the dinitrophenyl derivatives of the other protein amino acids, by partition chromatography on columns is described. 2. The harmful effect on resolving power of using too close-fitting a packing tool in preparing these partition columns is indicated and the dimensions needed to obtain good resolution are given.

FURTHER OBSERVATIONS ON THE PRODUCTION OF AMINO ACIDS BY RAT-LIVER MITOCHONDRIA AND OTHER SUBCELLULAR FRACTIONS

1. Rat-liver mitochondria showed a decrease in amino acid production after preparation in 0.25m-sucrose containing EDTA (1mm), but an increase in water content. When EDTA was replaced by Mn(2+) (1mm) or succinate (1mm), both amino acid production and water content were lowered, whereas preparation in 0.9% potassium chloride caused an increase in both. 2. Amino acid production by rat-liver homogenates prepared in 0.9% potassium chloride or 0.25m-sucrose was similar (q(amino acid) 0.047 and 0.042 respectively aerobically). After freezing-and-thawing q(amino acid) values were approximately doubled, and approached that of a homogenate prepared in water. 3. All cations tested inhibited amino acid production by mitochondria, Hg(2+) and Zn(2+) being the most effective in tris-hydrochloric acid buffer. In phosphate buffer Mg(2+) and Mn(2+) had no effect. Of the anions tested only pyrophosphate and arsenate had any inhibitory effect at final concn. 1mm. 4. Iodosobenzoate (1mm) and p-chloromercuribenzenesulphonate (1mm) inhibited mitochondrial amino acid production by 70-80%, whereas soya-bean trypsin inhibitor, EDTA and di-isopropyl phosphorofluoridate inhibited by a maximum of 30%. Respiratory inhibitors had no effect. 5. Rat-liver homogenate and subcellular fractions each showed an individual pattern of inhibition when a series of inhibitors was tested. 6. Amino acid production by mitochondria was decreased by up to 50% in the presence of oxidizable substrate, apart from alpha-glycerophosphate and palmitate, which had no effect. CoA stimulated amino acid production in tris-hydrochloric acid but not in phosphate buffer, alpha-oxoglutarate abolishing the stimulation. 7. Cysteine and glutathione stimulated amino acid production by whole mitochondria by 30%, but only reduced glutathione stimulated production in broken mitochondria. 8. Adrenocorticotrophic hormone and growth hormone stimulated mitochondrial amino acid production by 21-24%, whereas insulin inhibited production by 25%. 9. Coupled oxidative phosphorylation increased amino acid production by up to 154% at 25 degrees and 40 degrees . The increase was abolished by 2,4-dinitrophenol. 10. Amino acid incorporation in mitochondria was accompanied by an increase in amino acid production, both being decreased by chloramphenicol. 11. Mitochondrial production of ninhydrin-positive material was increased in the presence of albumin. The biggest increase was noted for the soluble fraction of broken mitochondria. No increase was found in the presence of (14)C-labelled algal protein or denatured mitochondrial protein.

GLYCYL-PROLINE IN URINE OF HUMANS WITH BONE DISEASE

An unknown ninhydrin-reacting substance has been found in the urine of three human subjects with rickets. A sample of the substance separated from urine by elution chromatography was hydrolyzed in acid, and equimolar amounts of glycine and proline were released. The DNP reaction applied to the substance resulted in DNP-glycine and free proline. The isolated unknown substance and glycyl-L-proline cochromatographed and coelectrophoresed in a number of solvent and buffer systems. The substance was therefore identified as glycyl-proline.Glycyl-proline is apparently excreted from plasma into urine; it is poorly absorbed by the kidney and its transport is independent of either the glycine or the L-proline transport mechanisms.Glycyl-proline was not excreted by normal subjects. It was found only in patients with severe active rickets. Glycyl-proline excretion paralleled that of total bound hydroxyproline, both diminishing as the rickets healed. Bone collagen appears to be the likely source for glycyl-proline in these patients.

PURIFICATION AND N-TERMINAL ANALYSES OF ALGAL BILIPROTEINS

1. R-, B- and C-phycoerythrins and R- and C-phycocyanins were isolated and purified on a preparative scale by calcium phosphate chromatography, ammonium sulphate fractionation and crystallization. 2. The N-terminal residues of these biliproteins were analysed. Methionine is the only N-terminal residue of all the phycoerythrins, there being about 14 N-terminal residues per molecule of R- and B-phycoerythrins (mol.wt. 290000) and about 8 per molecule of C-phycoerythrin (mol.wt. 226000). Threonine (1 residue) is N-terminal in C-phycocyanin (mol.wt. 138000), and both threonine (about 1.3 residues) and methionine (5 residues) are N-terminal in R-phycocyanin (mol.wt. 273000). 3. Results suggest that the apoproteins of the various phycoerythrins are closely related, whereas C-phycocyanin has quite a different gross structure, and that R-phycocyanin contains two types of sub-unit, one related to C-phycocyanin and the other to the phycoerythrins.