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PubMed1975

The mechanism of microtubule-dependent movement of pigment granules in teleost chromatophores.

The relationship of cytoplasmic microtubules to intracellular transport has been investigated in teleost chromatophores. Antimitotic agents, including colchicine, vinblastine, hydrostatic pressure, and low temperature remove microtubules in these cells and simultaneously disrupt the alignment and arrest the movement of pigment granules. During recovery, the return of alignment and movement corresponds in both time and space with the repolymerization of microtubules. These results demonstrate that microtubules are essential for the intracellular transport of pigment. Investigations of the mechanism of movement show that microtubules do not change in number or location during the redistribution of pigment in Fundulus melanophores. Microtubules in melanophores also behave as semi-stable organelles as determined by investigation with colchicine and hydrostatic pressure. These observations and others rule out a push-pull mechanism based on the polymerization and depolymerization of microtubules or one that distinguishes two operationally different sets of microtubules. It is proposed instead that particles move by sliding along a fixed array of microtubules.

Animals↗

PubMed1986

Localization of the exposed N-terminal region of the B800-850 alpha and beta light-harvesting polypeptides on the cytoplasmic surface of Rhodopseudomonas capsulata chromatophores.

Proteinase K and trypsin were used to determine the orientation of the light-harvesting B800-850 alpha and beta polypeptides within the chromatophores (inside-out membrane vesicles) of the mutant strain Y5 of Rhodopseudomonas capsulata. With proteinase K 7 amino acid residues of the B800-850 alpha polypeptide were cleaved off up to position Trp-7--Thr-8 of the N terminus, and 11 residues were cleaved off up to position Leu-11-Ser-12 of the beta chain N terminus. The C termini of the B800-850 alpha and beta polypeptides, including the hydrophobic transmembrane portions, remained intact. It is proposed that the N termini of the alpha and beta subunits, each containing one transmembrane alpha-helical span, are exposed on the cytoplasmic membrane surface and the C termini are exposed to or directed toward the periplasm.

Amino Acids↗

PubMedDate not supplied

Origin of the ATP formed during the light-dependent oxygen uptake catalyzed by Rhodospirillum rubrum chromatophores.

The oxygen uptake which is observed when Rhodospirillum rubrum chromatophores are illuminated under air and in the presence of reduced 2, 6-dichlorophenolindophenol (DCIP), 2, 3, 5, 6-tetra-methyl-P-phenylenediamine (diaminodurene, DAD) or N, N'-tetramethyl-p-phenylenediamine (TMDP) depends on the electron-donor concentration according to the equation of Michaelis-Menten. The apparent Km for the donor is lowered by the electron-transfer inhibitor 2-heptyl-4-hydroxyquinoline-N-oxide (HQNO) which causes therefore a stimulation of the rate of the reaction at non-saturating concentrations of the donors. In contrast, the ATP formation which takes place simultaneously to oxygen uptake does not show an enzyme-like dependence on donor concentration. Moreover it is inhibited by HQNO to a variable extent, depending on the particular donor present and on its concentration. Therefore it appears that the HQNO-sensitive phosphorylation is coupled to a cyclic flow which coexists and competes with the non-cyclic flow from donor to oxygen. In the presence of HQNO, substrates and uncouplers of ATP formation accelerate somewhat the rate of the oxygen uptake supported by reduced DCIP and DAD. Thus part of the HQNO-resistant phosphorylation seems to be associated with the non-cyclic flow from those tow donors to oxygen. The lack of stimulation by phosphorylation or by uncoupling of the TMPD-supported oxygen uptake does not permit a conclusion as to whether this reaction is coupled to ATP formation or not. Another part of the HQNO-resistant ATP formation is independent of the presence of oxygen and appears to be associated to cyclic flows which bypass the HQNO site. This type of phosphorylation is most important in the presence of TMPD.

Adenosine Triphosphate↗

PubMed1976

[Bacteriochlorophyll fluorescence changes related to the bacteriopheophytin photoreduction in the chromatophores of purple sulfur bacteria].

It is shown that illumination of chromatophores of sulfur bacterium Chromatium minutissimum at Eh of the medium --200 mV divided by --620 mV (when the photooxidation of pigment P890 is completely inhibited) induces a decrease in bacteriochlorophyll fluorescence yield, reversible in the dark. Under these conditions a reversible photoreduction of bacteriopheophytin is detected (bleaching of absorption bands at 543 and 760 nm and development of a band at 650 nm), which is accompanied by a blue shift of the absorption band at 8 nm. As a possible interpretation of these effects the suggestion is made on the function of bacteriopheophytin as a primary electron acceptor in reaction centers of bacteria. The bacteriopheophytin photoreduction, followed by a decrease in fluorescence yield, is also observed in other sulfur bacteria, Thiocapsa roseopersicina and Ectothiorodospira shaposhnikovii, but it is not detected in nonsulfur bacteria, Rhodospirillum rubrum and Rhodopseudomonas spheroides. This is considered as an evidence for the difference in the functional organization of the reaction centers of these two groups of bacteria,

Bacterial Chromatophores↗

PubMed1976

The beta adrenergic receptors of chromatophores of the frog, Rana pipiens.

The isolated skin of Rana pipiens was found to be a suitable model for the quantitative study of chromatophore beta adrenergic receptors uninfluenced by prejunctional phenomena. Cumulative concentration-response curves for adrenergic agonists were obtained in preparations in which effective alpha adrenergic blockade had been produced with phenoxybenzamine. The beta adrenergic agonists darkened the preparation, as did melanocyte-stimulating hormone, but the maximum effects differed. The maximum of the l-isoproterenol cumulative concentration-response curve was approximately 50% less than that of melanocyte-stimulating hormone, while the maxima for l-epinephrine and l-norepinephrine were significantly less than that for isoproterenol. Microscopic examination revealed a qualitative difference: while maximal darkening produced by melanocyte-stimulating hormone was associated with maximal changes in both interspot melanophores and iridophores, maximal adrenergic-induced darkening was associated with maximal iridophore granule concentration only. No qualitative differences could be observed in the darkening caused by the three adrenergic agonists. The beta adrenergic potencies of l-norepinephrine and l-isoproterenol relative to l-epinephrine were determined by four-point bioassay. Isoproterenol was found to be 138 times as potent as epinephrine, while norepinephrine was 4 times as potent. Similarly, antagonism of isoproterenol-induced darkening of phenoxybenzamine-pretreated skin samples by the beta adrenergic blocking agents dl-propranolol, dl-sotalol, dl-practolol, l-butoxamine and d-butoxamine was studied, and their KB and pA2 values, respectively, were found to be: dl-propranolol (1.44 X 10(-8)M, 7.81); dl-sotalol (7.25 X 10(-8)M, 7.23); l-butoxamine (6.92 X 10(-6)M, 5.10); dl-practolol (1.91 X 10(-5)M, 4.96); d-butoxamine (no activity). Comparison of the potency ratios and pA2 values cited above with similar parameters obtained by other investigators in several mammalian tissues suggests that there is wide variation among beta adrenergic receptors.

Adrenergic beta-Agonists↗

PubMedDate not supplied

[Spectral position of the principal absorption band of pigment complex P870 and the kinetics of photo-induced oxidoreductions in the reaction centers and chromatophores of purple bacteria with preparations at different temperatures and having different degrees of hydration].

In isolated photosynthetic reaction centres of Rps. spheroides and chromatophores R. rubrum the spectral position of the longest wavelength absorption band of P870, effectiveness of electron removal from the photochemical pair (P870 -- primary electron acceptor, A1) and the rate constant for recombination of photooxidized P870 with photoreduced A1 undergo marked and fully reversible changes over the temperature interval from +20 to -70 degrees. Dehydration of the samples has the effect similar to that induced by temperature lowering. The data suggest that the spectral position of the main maximum of pigment complex P870 absorption band may be regarded as a sensitive inner probe of the structure-functional state of the investigated preparations.

Bacterial Chromatophores↗

PubMedDate not supplied

[Effect of temperature on the phototransformation of purple sulfur bacteria bacteriochlorophylls and isolated chromatophores].

Photobleaching of P890 was shown to be independent of temperature within the range of +20 to -160 degrees C in purple sulphur bacteria and isolated chromatophores under oxidative conditions; therefore changes in the absorption at 890 nm are due to the primary photoact. No changes were detected in the absorption at 850 nm upon a slight decrease of temperature, which suggested the absorption at 850 nm upon a slight decrease of temperature, which suggested the conformation nature of these changes. The effect of temperature, which suggested the conformation nature of these changes. The effect of temperature on the photoinduced changes of absorption under reductive conditions seems to be due to the electron transport and the accompanying processes being blocked. The effect of temperature on the kinetics of P890+ reduction in the darkness under conditions when the cytochromes are preliminarily oxidized is determined by the participation of the secondary electron acceptors in this process. A decrease in temperature leads to blocking the transport of electrons from the primary acceptor to the secondary acceptors, which is expressed by a gradual disappearance of a slow component in the kinetics of p890+ reduction in the disappearance of a slow component in the kinetics of P890+ reduction in the darkness and by the intensification of a fast component resulting from the darkness and by the intensification of a fast component resulting from the interaction between the primary acceptor and P890+. Methodical aspects of absorption differential spectrophotometry of photosynthesizing organisms at low temperatures are discussed.

Bacteria↗

PubMed2001

Effect of water extract of the bark of Buchanania lanzan linn. on behaviour and chromatophores of a fresh water fish, Labeo rohita.

Fish exposed to 150 ppm and 250 ppm doses saparately, showed eratic swimming with hyper-excitability, spiralling, convulsion and mortality. However at 350 ppm dose fish became lethargic and steady at the bottom of aquarium. This behaviour appears to be due to sedative effects of fish implicating the phychoactive nature of the plant B. Ianzan. At 150 ppm to 350 ppm doses, fish scale changed from reticulate to punctate chromatophores; and treated fish when transferred to fresh water, were slowly regained to normal behaviour after 96 h exposure. Hence doses regaining from 150 ppm to 350 ppm is considered to be psychoative in nature. In higher doses 450 ppm and 550 ppm fish could survive only 76 h and 4.30 h respectively and then died indicating toxicity of plant for the said doses. It is found that scale present on its body is most suitable test system for the study of psychoactivity and toxicity of plant extracts on fish, Labeo rohita.

Anacardiaceae↗

PubMed1977

[Purification and properties of phototrophic bacteria Thiocapsa roseopersicina hydrogenase bound with chromatophores].

The method of solution and puridication of hydrogenase from chromatophores of purpur sulphur bacteria Thiocapsa roseopersicina strain BBS are described. Hydrogenase molecular weight is 73000. It contains 4,4 mole S2- and 3.1 mole Fe2+ per mole of protein; pI 4.15. The enzyme absorption spectrum has the maximun et 400-410 nm, which is characteristic of proteins containing non-haem iron. Membrane--linked enzyme as well as soluble hydrogenase of that microorganism is characterized by high thermal stability: inactivation occurs at the temperature above 78 degrees C when the optimal temperature for that enzyme is 70 degrees C. Homogenous enzyme catalyses D2--H2O exchange reaction, reversible redox reaction of methyl viologene and benzyl viologene.

Bacterial Chromatophores↗

PubMedDate not supplied

[Polyphosphate biosynthesis in Rhodospirillum rubrum chromatophores].

The chromatophores of Rhodospirillum rubrum were found to synthesize in the light not only ATP and pyrophosphate but also high molecular weight polyphosphates. Biosynthesis of all studied compounds was inhibited by antimycin A, an inhibitor of the electron-transport photosynthetic chain. Synthesis of high molecular weight polyphosphates is stimulated, while that of pyrophosphate is inhibited, in the conditions providing intensive synthesis of ATP (in the presence of ADP and in the absence of oligomycin). The results obtained suggest that biosynthesis of high molecular weight polyphosphates is related to photosynthetic phosphorylation, via ATP but not pyrophosphate.

Adenosine Diphosphate↗

PubMedDate not supplied

[EPR study of redox titration of Chromatium minutissimum chromatophores].

Redox titration of chromatophores through the region +300 +570 mV at room temperature results in generation of two dark ESR signals, a well-known reaction center signal and a new narrow line. This line is characterized by deltaH pp = 4.2 Oe, g-factor about that of RC and a Lorentzian shape. It is insensitive to illumination. The determination of an RC signal midpoint potential is affected by the presence of the narrow line. Taking into account the superposition of the two ESR signals it was measured to be +(486+/-+/-18)mV.

Bacterial Chromatophores↗

PubMed1989

Coupling of ATP hydrolysis to phosphate uptake in Rhodospirillum rubrum chromatophores under the influence of Ca2+ and Mg2+.

The Pi-ATP exchange and ATP hydrolytic reactions, by the F0F1 complex, were studied in Rhodospirillum rubrum chromatophores in the dark. An optimal pH between 7.0 and 8.5 was determined for the hydrolytic and exchange reactions. Under these conditions, the hydrolysis/exchange ratio was approximately 2. The kinetic analysis of the hydrolytic and exchange reactions using Mg-ATP as substrate showed a change in the hydrolysis/exchange ratio that varied between 2.0 and 2.8 as the substrate concentration was increased. With Ca-ATP, hydrolysis was not saturated up to a substrate concentration of 5.0 mM, and the hydrolysis/exchange ratios changed from 2 to 240 as the substrate concentration was increased from 0.06 to 5.0 mM. Free Mg2+ inhibited hydrolysis and phosphate uptake without altering the hydrolysis/exchange ratio. Nigericin induced an increase in the hydrolysis/exchange ratio from 2.7 to 130, whereas in the presence of valinomycin, this ratio increased from 2.7 to 21. From these results, it can be concluded that Ca-ATP hydrolysis is loosely coupled to phosphate uptake given that Pi-ATP exchange activity is extremely low, even at high rates of ATP hydrolysis.

Adenosine Triphosphate↗

PubMed1985

Control of chromatophore movements in dermal chromatic units of blue damselfish--I. The melanophore.

Mechanisms controlling pigment movements in the melanophore of the blue damselfish, Chrysiptera cyanea, were studied. Histological observations revealed that the melanophore had three-dimensionally developed processes to envelop overlying small iridophores, and thus participated in the construction of a simple dermal chromatophore unit. Nervous stimulation, catecholamines and melatonin brought about melanosome aggregation in the melanophore. The actions of the nervous stimulation and catecholamines were antagonized by alpha adrenolytic agents. A beta adrenergic agonist, metaproterenol, adenosine and adenine nucleotides, and alpha-MSH acted as pigment-dispersing agents. These results indicate that the melanophore of the present material is controlled quite orthodoxly by adrenergic nerves and endocrines, notwithstanding the fact that it has quite a unique morphology among fish species, and that its motile rate is remarkably high.

Animals↗

PubMed1985

ATP synthesis and hydrolysis by a hybrid system reconstituted from the beta-subunit of Escherichia coli F1-ATPase and beta-less chromatophores of Rhodospirillum rubrum.

Photophosphorylation and ATPase activities were restored to beta-less Rhodospirillum rubrum chromatophores by their reconstitution with purified beta-subunits of either R. rubrum F1-ATPase (Rr beta) or Escherichia coli F1-ATPase (Ec beta). In the homologous reconstituted system both activities were restored to the same extent, whereas in the hybrid system ATP synthesis was restored to about 10% when the hydrolysis was restored to 200%. This difference in rates of synthesis and hydrolysis was not due to any general uncoupling effect of Ec beta leading to an increased membrane permeability to protons, because with both hybrid and homologous systems an identical light-induced quenching of quinacrine fluorescence was observed. They differed, however, in ATP-driven quenching of quinacrine fluorescence, which was much lower in the hybrid system. These results suggest that the hybrid has a decreased capacity for proton-translocation through the membrane-bound Fo channel during ATP hydrolysis, and probably also during ATP synthesis. The very high ATPase activity of the hybrid system indicates that it might enable the released protons to leak to the outside medium rather than to move inside through the Fo channel. The activities restored by Rr beta and Ec beta exhibit a similar sensitivity to dicyclohexylcarbodiimide, but different sensitivities to oligomycin and to an anti-E. coli F1 (EcF1) antibody. Oligomycin inhibited only the homologous R. rubrum system whereas anti-EcF1 was a much more effective inhibitor of the hybrid system. It is therefore concluded that Rr beta plays a role, that the Ec beta cannot fulfill, in conferring oligomycin sensitivity to the RrFo X F1-ATP synthase-ATPase complex.

Adenosine Triphosphate↗

PubMedDate not supplied

[Activation and inhibition of photoinduced proton absorption in Rhodospirillum rubrum chromatophores by detergents and solvents].

The effects of detergents (Triton X-100) and solvents (diethyl ether, metanol) on the reversible light-induced proton uptake, photophosphorylation and band shift of the carotenoid in chromatophores from R. rubrum are described. All these compounds were found to stimulate the extent of light-induced proton uptake with subsequent inhibition when the concentrations were increased. Stimulation of proton uptake is accompanied by inhibition of both phosphorylation and carotenoid absorbance shift.

Bacterial Chromatophores↗

PubMed1983

[Effect of 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone, a ubiquinone analog, and SH-reagents on the electrogenic function of pyrophosphatase from Rhodospirillum rubrum chromatophores].

Inorganic pyrophosphate-induced membrane potential generation in Rhodospirillum rubrum chromatophores is inhibited by 2,5-dibromo-2-methyl-6-isopropyl-p-benzoquinone (DBMIB). The inhibition is increased by menadione and dithionite and is not relieved by ascorbate; this effect is probably due to a displacement of the intrachromatophore quinones by DBMIB. The SH-reagents, N-ethylmaleimide and p-chloromercurybenzoate at high concentrations inhibit membrane potential generation driven by inorganic pyrophosphate hydrolysis, thus suggesting the involvement of SH-groups in pyrophosphatase operation. The mechanism of regulation of the mode of action of pyrophosphatase by quinones and the location of the SH-groups of the enzyme are discussed.

Bacterial Chromatophores↗

PubMedDate not supplied

[Thermodynamic characteristics of the interaction of high-potential cytochrome with dimer of bacteriochlorophyll in the reaction centers of Ectothiorhodospira shaposhnikovii chromatophores].

Kinetics of dark reduction of cytochrome CH (E7=290 mV) after its photoinduced oxidation chromatophores of E. shaposhnikovii at 110-210 K is analysed. A ratio is derived which describes dark reduction of cytochrome. This ratio makes it possible to determine the value of free energy of the electron transfer between cytochrome and bacteriochlorophyll dimer of the reaction centre (Bchl)2. The values of enthalpy and entropy of the transition under study at the temperatures below 210 K are equal to 1,67 kJ M-1 and 26,8 J M-1 K-1 correspondingly. A change of free energy obtained by linear extrapolation to the room temperature equals 9,71 kJ M-1. This value well agrees with the value 9,63 kJ M-1 obtained from the results of direct potentiometric titration of photoinduced redox transformations CH and (Bchl)2.

Bacterial Chromatophores↗

PubMed1981

Local light stimulation of isolated chromatophores of the sea urchin Centrostephanus longispinus.

The dark-reaction (pigment aggregation) of isolated, light-sensitive pigment cells of the sea urchin Centrostephanus longispinus was monitored using IR-microscopy. It differs in time course and mode of pigment displacement from the inverse process of pigment dispersion in white light. Partial illumination of darkness respectively causes locally different and appropriate pigment movements in the individual cell regions. Spot-illumination of a cell process of an otherwise darkened chromatophore leads to local pigment dispersion (from thd dark-adapted state) or aggregation (from the light-adapted state) exactly to the point of stimulation, while the pigment cell shows normal dark-reaction in all other regions. The results indicate that the pigment granules do not bear the receptor pigment, rather it may be expected in the whole cell membrane. The observation of contrary translocations in different regions of the cell support the concept of a local mechanism of granule movement regulated in a very precise manner.

Animals↗