A partial sequence of ionic changes associated with the acrosome reaction of Strongylocentrotus purpuratus

Relationships among several of the ion movements associated with the acrosome reaction of S. purpuratus were investigated. Egg jelly initiates ⁴⁵Ca²⁺ and ²²Na⁺ uptake, and K⁺ and H⁺ efflux. H⁺ efflux and ²²Na⁺ uptake occur with approximately equivalent stoichiometries as rapidly as the appearance of acrosomal rods, perhaps reflecting a linked process. Most K⁺ loss, as measured either by ⁴²K⁺ efflux or K⁺-ion-selective electrodes, occurs after the acrosome reaction is complete. Since an elevation of seawater K⁺ (from 10 to 15 mM) or the addition of 0.5 mM tetraethylammonium (TEA), an inhibitor of K⁺ channels, inhibits the acrosome reaction half-maximally, K⁺ movements or alterations of K⁺-dependent membrane potentials may regulate the triggering by jelly. Most, but not all, of the ⁴⁵Ca²⁺ influx is inhibited with a mixture of 10 μM FCCP, 1 mM CN^?, and 2 μg/ml oligomycin, suggesting that the mitochondria store most of the Ca²⁺. The extracellular Na⁺ concentration affects Ca²⁺ fluxes: sperm placed into 5 mM Na⁺ seawater have enhanced ⁴⁵Ca²⁺ uptake, but do not undergo the acrosome reaction, unless 30 mM Na⁺ is also added. Low Na⁺ concentrations lead to spontaneous triggering, by allowing for both Ca²⁺ influx and Na⁺-dependent H⁺ efflux. At least one early Ca²⁺ requirement precedes the Na⁺ and H⁺ movements, as inferred from attempts at reversing the inhibitors of jelly induction of the acrosome reaction. When sperm are incubated with jelly in the absence of Ca²⁺, then washed and incubated with jelly in the presence of Ca²⁺, the acrosome reaction is triggered only upon the second incubation. However, when sperm are mixed with jelly in the presence of the other inhibitors (verapamil, TEA, 5 mM Na⁺ seawater, low pH, or elevated K⁺), they are altered so that even upon subsequent washing, jelly-mediated triggering is no longer possible. This suggests the existence of an intermediate state in the reaction pathway, that follows an event for which Ca²⁺ is required, but that precedes the Na⁺ and H⁺ movements, which are inhibited by all inhibitors of the acrosome reaction. These data are used to develop a partial sequence of ionic changes associated with the triggering mechanism.     

Reversible uncoupling of energy transfer between phycobilins and chlorophyll in Anacystis nidulans. Light stimulation of cold-induced phycobilisome detachment

Phycobilin fluorescence of Anacystis nidulans grown at 28°C increases substantially upon cooling below 10°C. A maximal increase is found around ?5°C and amounts to 300%, with almost complete reversibility upon re-warming. Illumination with actinic light leads to considerable stimulation of the cold-induced phycobilin fluorescence increase. Analysis of the light stimulation phenomenon reveals: (1) Actinic illumination shifts the fluorescence-temperature characteristic by about 3°C upwards on the T-axis. At temperatures below 5°C the light stimulating effect becomes smaller again and fluorescence-temperature characteristics measured at high and low light intensity converge around ?5°C. (2) In the 13-8°C region a large (up to 100%) light-induced phycobilin fluorescence increase is observed, while only negligible changes occur in the dark. (3) 3-(3,4-Dichlorophenyl)-1,1-dimethyl urea (DCMU) as well as uncouplers inhibit the light stimulation, which hence depends on coupled electron transport.In agreement with previous work (Schreiber, U. (1979) FEBS Lett. 107, 4–9) it is concluded that illumination enhances cold-induced phycobilisome detachment by increasing the net negative charge at the outer surface of the thylakoid membrane. The possible role of a fluid → ordered transition of membrane lipids (Murata, N. and Fork, D.C. (1975) Plant Physiol. 56, 791–796) is discussed.     

Control of activity states of heart mitochondrial ATPase. Role of the proton-motive force and Ca2+

The ATPase complex of submitochondrial particles exhibits activity transitions that are controlled by the natural ATPase inhibitor (Gómez-Puyou, A., Tuena de Gómez-Puyou, M. and Ernster, L. (1979) Biochim. Biophys. Acta 547, 252–257). The ATPase of intact heart mitochondria also shows reversible activity transitions; the activation reaction is induced by the establishment of electrochemical gradients, whilst the inactivation reaction is driven by collapse of the gradient. In addition it has been observed that the influx of Ca²⁺ into the mitochondria induces a rapid inactivation of the ATPase; this could be due to the transient collapse of the membrane potential in addition to a favorable effect of Ca²⁺-ATP on the association of the ATPase inhibitor peptide to F₁-ATPase. This action of Ca²⁺ may explain why mitochondria utilize respiratory energy for the transport of Ca²⁺ in preference to phosphorylation. It is concluded that the mitochondrial ATPase inhibitor protein may exert a fundamental regulatory function in the utilization of electrochemical gradients.     

NADH: Nitrate reductase activity restoration by rhodanese

The NADH: nitrate reductase from durum wheat leaves was inactivated by cyanide and its activity restored by thiosulphate and beef kidney rhodanese. Rhodanese and thiosulphate, added to NADH-nitrate reductase before cyanide treatment protected NADH-nitrate reductase activity. No oxidizing agent was required for the protection or restoration of cyanide treated NADH-nitrate reductase.     

Generation of electric current by chromatophores of Rhodospirillum rubrum and reconstitution of electrogenic function in subchromatophore pigment-protein complexes

Lipoprotein complexes, containing (1) bacteriochlorophyll reaction centers, (2) bacteriochlorophyll light-harvesting antenna or (3) both reaction centers and antenna, have been isolated from chromatophores of non-sulphur purple bacteria Rhodospirillum rubrum by detergent treatments. The method of reconstituting the proteoliposomes containing these complexes is described. Being associated with planar azolectin membrane, proteoliposomes as well as intact chromatophores were found to generate a light-dependent transmembrane electric potential difference measured by Ag/AgCl electrodes and voltmeter. The direction of the electric field in proteoliposomes can be regulated by the addition of antenna complexes to the reconstitution mixture. The reaction center complex proteoliposomes generate an electric field of a direction opposite to that in chromatophores, whereas proteoliposomes containing reaction center complexes and a sufficient amount of antenna complexes produce a potential difference as in chromatophores. ATP and inorganic pyrophosphate, besides light, were shown to be usable as energy sources for electric generation in chromatophores associated with planar membrane.     

Inhibition of energy-transducing functions of chloroplast membranes by lipophilic iron chelators

Lipophilic metal chelators inhibit various energy-transducing functions of chloroplasts. The following observations were made.1. Photophosphorylation coupled to any known mode of electron transfer, i.e. whole-chain noncyclic, the partial noncyclic Photosystem I or Photosystem II reactions, or cyclic, is inhibited by several lipophilic chelators, but not by hydrophilic chelators.2. The light- and dithioerythritol-dependent Mg²⁺-ATPase was also inhibited by the lipophilic chelators.3. Electron transport through either partial reaction, Photosystem I or Photosystem II was not inhibited by lipophilic chelators. Whole-chain coupled electron transport was inhibited by bathophenanthroline, and the inhibition was not reversed by uncouplers. The diketone chelators diphenyl propanedione and nonanedione inhibited the coupled, whole-chain electron transport and the inhibition was reversed by uncouplers, a pattern typical of energy transfer inhibitors.The electron transport inhibition site is localized in the region of plastoquinone → cytochrome f. This inhibition site is consistent with other recent work (Prince et al. (1975) FEBS Lett. 51, 108 and Malkin and Aparicio (1975) Biochem. Biophys. Res. Commun. 63, 1157) showing that a non-heme iron protein is present in chloroplasts having a redox potential near +290 mV. A likely position for such a component to function in electron transport would be between plastoquinone and cytochrome f, just where our data suggests there to be a functional metalloprotein.4. Some of the lipophilic chelators induce H⁺ leakiness in the chloroplast membrane, making interpretation of their phosphorylation inhibition difficult. However, 1–3 mM nonanedione does not induce significant H⁺ leakiness, while inhibiting ATP formation and the Mg²⁺-ATPase. Nonanedione, at those concentrations, causes a two- to four-fold increase in the extent of H⁺ uptake.5. These results are consistent with, but do not prove, the involvement of a non-heme iron or a metalloprotein in chloroplast energy transduction.     

Rapid stimulation of K -H exchange by a plant growth hormone.

The growth-promoting phytotoxin fusicoccin¹ stimulates both [⁸⁶Rb⁺]K⁺ uptake and H⁺-excretion from oat coleoptiles by at least 5-fold after a lag of less than 90 seconds. Both processes are affected similarly by metabolic inhibitors and external pH. FC appears to activate a K⁺H⁺ exchange which is only partly specific for K⁺, and which can transport more H⁺ than K⁺. The natural plant growth hormone indoleacetic acid¹ also stimulates K⁺-uptake, but only after a long lag, and to a maximum of 30%, suggesting that IAA does not affect directly the K⁺H⁺ exchange process, and that the two hormones induce H⁺-excretion, and thus cell elongation, by different mechanisms.     

Bioremoval of Cyanide and Phenol from Industrial Wastewater: An Update

In nature, phenols and cyanides are produced by certain microbes and plants. Phenols are antioxidants found in almost all plants, and cyanides are important components of lima beans, almonds, and cassava. Their presence in small amounts may not upset the environment, but their large-scale production, wide applicability, and unrestricted release by the industries makes them widespread and important pollutants. Phenols and cyanides can be recovered/removed from wastewater streams using various physicochemical techniques practiced commercially. Lack of complete mineralization, cost-effectiveness, and release of secondary by-products are amongst a few of the major considerations that limit the installation of such processes. Biological removal of such pollutants from industrial waste has gained momentum in recent years, as they promise to surpass the major drawbacks laid by the physicochemical methods and can be practically carried out in all conditions. Presence of either cyanide or phenol is highly dangerous, and in the presence of both, the effect is compounded. The present review illustrates the various industries involved in the release of phenols, cyanides, or both; it summarizes the available technologies for their treatment and emphasizes recent advances and advantages of biological abatement of these pollutants.     

Inactivation of Rabbit Liver Carbonyl Reductase by Phenylglyoxal and 2,3,4-Trinitrobenzenesulfonate Sodium

The chemical modifications of rabbit liver carbonyl reductase (RLCR) with phenylglyoxal (PGO) and 2,3,4-trinitrobenzenesulfonate sodium (TNBS), which are respective chemical modifiers of arginine and lysine residues, were examined. RLCR was rapidly inactivated by these modifiers. Kinetic data for the inactivation demonstrated that each one of arginine and lysine residues is essential for catalytic activity of the enzyme. Furthermore, based on the protective effects of NADP +, NAD + and their constituents against the inactivation of RLCR by PGO and TNBS, we propose the possibility that the functional arginine and lysine residues are located in the coenzyme-binding domain of RLCR and interact with the 2′-phosphate group of NADPH.