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PubMed1979

Blue and red shifts of bacteriochlorophyll absorption band around 880 nm in Rhodospirillum rubrum.

The redox potential dependence of the light-induced absorption changes of bacteriochlorophyll in chromatophores and subchromatophore pigment-protein complexes from Rhodospirillum rubrum has been examined. The highest values of the absorption changes due to the bleaching of P-870 and the blue shift of P-800 in chromatophores and subchromatophore complexes are observed in the 360-410mV redox potential range. At potentials below 300 mV (pH 7.0), the 880 nm band of bacteriochlorophyll shifts to shorter wavelengths in subchromatophore complexes and to longer wavelengths in chromatophores. The data on redox titration show that the red and blue shifts of 880-nm bacteriochlorophyll band represent the action of a non-identified component (C340) which has an oxidation-reduction midpoint potential close to 340 mV (n=1) at pH 6.0--7.6. The Em of this component varies by 60 mV/pH unit between pH 7.6 and 9.2. The results suggest that the red shift is due to the transmembrane, and the blue shift to the local intramembrane electrical field. The generation of both the transmembrane and local electrical fields is apparently governed by redox transitions of the component C340.

Bacterial Chromatophores↗

PubMed1980

Identification of the carotenoid present in the B-800-850 antenna complex from Rhodopseudomonas capsulata as that which responds electrochromically to transmembrane electric fields.

Mild proteolysis of Rhodopseudomonas capsulata chromatophores results in a parallel loss of the 800 nm bacteriochlorophyll absorption band a blue shift in the carotenoid absorption bands associated with the B-800-850 light-harvesting complex. Both the light-induced and the salt-induced electrochromic carotenoid band shift disappear in parallel to the loss of the 800 nm bacteriochlorphyll absorption upon pronase treatment of chromatophores. During the time required for the loss of the 800 nm bacteriochlorophyll absorption and the loss of the electrochromic cartenoid band shift photochemistry is not inhibited and the ionic conductance of the membrane remains very low. We conclude that the carotenoid associated with the B-800-850 light-harvesting complex is the one that responds electrochromically to the transmembrane electric field. Analysis of the pigment content of Rps. capsulata chromatophores indicates that all of the carotenoid may be accounted for in the well defined pigment-protein complexes.

Bacterial Chromatophores↗

PubMed1980

Correlation of membrane-potential-sensing carotenoid to pigment-protein complex II in Rhodopseudomonas sphaeroides.

The changes in carotenoid absorbance induced by illumination or by a diffusion potential were larger in chromatophores from cells cultured under low light intensity than those in chromatophores from high-light culture in a photosynthetic bacterium, Rhodopseudomonas sphaeroides. The carotenoid molecules which are associated with the pigment-protein complex (with the infrared bacteriochlorophyll peaks at 800 and 850 nm) (complex II) probably respond to the electrical field changes in the chromatophore membrane.

Bacterial Chromatophores↗

PubMed1979

Membranes of Rhodopseudomonas sphaeroides. VI. Isolation of a fraction enriched in newly synthesized bacteriochlorophyll alpha-protein complexes.

Radioactivity eventually destined for the chromatophore membrane of Rhodopseudomonas sphaeroides was shown in pulse-chase studies to appear first in a distinct pigmented fraction. The material formed an upper pigmented band which sedimented more slowly than chromatophores when cell-free extracts were subjected directly to rate-zone sedimentation on sucrose density gradients. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that the purified fraction contained polypeptide bands of the same mobility as light-harvesting bacteriochlorophyll alpha and reaction center-associated protein components of chromatophores; these were superimposed upon cytoplasmic membrane polypeptides. The pulse-chase relation was confined mainly to the polypeptide components of these pigment-protein complexes. It is suggested that the isolated fraction may be derived from sites at which new membrane invagination is initiated.

Bacterial Chromatophores↗

PubMed1986

Organization of the motor neuron components of the pallial nerve in octopus.

Following horseradish peroxidase (HRP) and cobalt (CO2+) application to the pallial nerve of two species of octopus, neurons that control various aspects of mantle behaviors were located in several lobes of the three main regions of the central brain. In the subesophageal region, cells were labeled in the anterior chromatophore, posterior chromatophore, palliovisceral, pedal and vasomotor lobes; in the superior buccal lobe of the supraesophageal region; and in the magnocellular lobe of the periesophageal region. Localization of labeled cells in and around both the anterior and posterior chromatophore lobes suggests a modification of the idea that a single functional area is solely located in an anatomically defined brain lobe of a cephalopod.

Animals↗

PubMed1966

Effect of lipids and organic solvents on the enzymic formation of zinc protoporphyrin and haem.

1. Differences observed in earlier work between the enzymic chelation with protoporphyrin of Zn(2+) and Fe(2+) ions respectively have now been explained as being caused by the presence of peroxides in the ether used in the enzyme assay. The inhibitory effect of peroxides is established by the reducing agent, which is present in the assay for chelation of iron but not in that for zinc. There are now no reasons for the belief that two different enzymes catalyse formation of complexes with zinc and iron respectively. 2. Removal of lipid from both chromatophores and mitochondria markedly reduced chelatase activity. Activity could be partially restored by the addition of lipid fractions. Phosphatidic acid, but not phosphatidylcholine or phosphatidylethanolamine, actively stimulated the formation of zinc protoporphyrin and haem by chromatophores and mitochondrial preparations. 3. Lipid-containing extracts of chromatophores, and fractions thereof obtained by silicic acid chromatography, partially restored chelatase activity of Tween extracts of mitochondria. Thus, although both enzymes are considered to be lipoproteins, the identity of the lipids concerned is still uncertain. 4. A great number of organic solvents such as esters, ethers, ketones and, to a lesser extent, alcohols, stimulate enzymic chelation of both metals with protoporphyrin. A number of explanations for these findings are considered and it is suggested that organic solvents interact in some way with the enzyme lipoprotein, changing either its conformation or allowing closer contact between the enzyme and its substrates.

Acetates↗

PubMed2000

Hybrid Rhodospirillum rubrum F(0)F(1) ATP synthases containing spinach chloroplast F(1) beta or alpha and beta subunits reveal the essential role of the alpha subunit in ATP synthesis and tentoxin sensitivity.

Trace amounts ( approximately 5%) of the chloroplast alpha subunit were found to be absolutely required for effective restoration of catalytic function to LiCl-treated chromatophores of Rhodospirillum rubrum with the chloroplast beta subunit (Avital, S., and Gromet-Elhanan, Z. (1991) J. Biol. Chem. 266, 7067-7072). To clarify the role of the alpha subunit in the rebinding of beta, restoration of catalytic function, and conferral of sensitivity to the chloroplast-specific inhibitor tentoxin, LiCl-treated chromatophores were analyzed by immunoblotting before and after reconstitution with mixtures of R. rubrum and chloroplast alpha and beta subunits. The treated chromatophores were found to have lost, in addition to most of their beta subunits, approximately a third of the alpha subunits, and restoration of catalytic activity required rebinding of both subunits. The hybrid reconstituted with the R. rubrum alpha and chloroplast beta subunits was active in ATP synthesis as well as hydrolysis, and both activities were completely resistant to tentoxin. In contrast, a hybrid reconstituted with both chloroplast alpha and beta subunits restored only a MgATPase activity, which was fully inhibited by tentoxin. These results indicate that all three copies of the R. rubrum alpha subunit are required for proton-coupled ATP synthesis, whereas for conferral of tentoxin sensitivity at least one copy of the chloroplast alpha subunit is required together with the chloroplast beta subunit. The hybrid system was further used to examine the effects of amino acid substitution at position 83 of the beta subunit on sensitivity to tentoxin.

Adenosine Triphosphate↗

PubMed2004

The H(+)-pyrophosphatase of Rhodospirillum rubrum is predominantly located in polyphosphate-rich acidocalcisomes.

Acidocalcisomes are acidic, calcium storage compartments with a H(+) pump located in their membrane that have been described in several unicellular eukaryotes, including trypanosomatid and apicomplexan parasites, algae, and slime molds, and have also been found in the bacterium Agrobacterium tumefaciens. In this work, we report that the H(+)-pyrophosphatase (H(+)-PPase) of Rhodospirillum rubrum, the first enzyme of this type that was identified and thought to be localized only to chromatophore membranes, is predominantly located in acidocalcisomes. The identification of the acidocalcisomes of R. rubrum was carried out by using transmission electron microscopy, x-ray microanalysis, and immunofluorescence microscopy. Purification of acidocalcisomes using iodixanol gradients indicated co-localization of the H(+)-PPase with pyrophosphate (PPi) and short and long chain polyphosphates (polyPs) but a lack of markers of the plasma membrane. polyP was also localized to the acidocalcisomes by using 4',6'-diamino-2-phenylindole staining and identified by using 31P NMR and biochemical methods. Calcium in the acidocalcisomes increased when the bacteria were incubated at high extracellular calcium concentrations. The number of acidocalcisomes and chromatophore membranes as well as the amounts of PPi and polyP increased when bacteria were grown in the light. Taken together, these results suggest that the H(+)-PPase of R. rubrum has two distinct roles depending on its location acting as an intracellular proton pump in acidocalcisomes but in PPi synthesis in the chromatophore membranes.

Bacterial Chromatophores↗

PubMed1965

The photosynthetic apparatus of Rhodospirillum molischianum.

By varying the light intensity and temperature during growth it is possible to obtain cultures of Rhodospirillum molischianum in which the specific bacteriochlorophyll contents differ by as much as fivefold. We used such cultures to compare the changes in the electron microscopic appearance of the cells with the changes in the amount and bacteriochlorophyll content of chromatophore material isolated from cell extracts. The cells contained a variable number of internal membranes which are invaginations of the cell membrane. The shape, size, number, and arrangement of the infoldings varied as the specific bacteriochlorophyll content of the cells changed. In cells with little bacteriochlorophyll, the invaginations were mostly tubular. In cells with larger amounts of bacteriochlorophyll, the invaginations were disc-shaped and the discs were appressed together in stacks of 2 to 10 discs each. Variations in the number of discs per stack could be accounted for by a simple statistical model. The average area per disc increased with increasing bacteriochlorophyll content. Quantitative estimations of the relative volumes occupied by membranes in cells with four different bacteriochlorophyll contents showed that the amount of internal membrane alone had no direct relationship with the bacteriochlorophyll content of the cells; however, the total amount of membrane (cell membrane plus internal membrane) was directly proportional to the bacteriochlorophyll content. The specific bacteriochlorophyll content of isolated chromatophore material was proportional to the bacteriochlorophyll content of whole cells; the total amount of chromatophore material was independent of the bacteriochlorophyll content of whole cells. Several possible explanations of this paradoxical discrepancy between the electron microscope observations and the analytical results are discussed.

Bacterial Chromatophores↗

PubMed1981

Fast stages of photoelectric processes in biological membranes. III. Bacterial photosynthetic redox system.

Chromatophores of photosynthetic bacteria Rhodospirillum rubrum, Rhodopseudomonas sphaeroides and Chromatium minutissimum were associated with a collodion film impregnated with a decane solution of asolectin. A very short light flash inducing a single turnover of the chromatophore photosynthetic redox system was found to induce the formation of an electrical potential difference amounting to 60 mV, directed across the film as measured with an orthodox electrometer technique. The main phase of the photoelectric response had a tau value of less than 200 ns. Addition of menadione and some other redox mediators increases the main phase amplitude and induces a slower phase (tau = 200 microseconds). In Ch. minutissimum chromatophores that retained their endogenous cytochrome c pool, one more electrogenic phase was revealed (tau = 20 microseconds). Redox titrations of the electric response and bacteriochlorophyll absorption at 430 nm as well as measurements of the kinetics of cytochrome c oxidation have indicated that the fastest electrogenic phase is due to electron transfer from bacteriochlorophyll to Fe-ubiquinone, the 20-microseconds phase to cytochrome c2+ - bacteriochlorophyll+ oxidoreduction, and the 200-microseconds phase to Fe-ubiquinone- oxidation by a secondary quinone. In the decay of the photoelectric response, a 30-ms phase was identified which was explained by a reverse electron transfer from reduced Fe-ubiquinone to oxidated bacteriochlorophyll. The difference in the fast kinetics of photoelectric generation by the bacteriochlorophyll system from those by bacterial and animal rhodopsins has been discussed.

Ascorbic Acid↗

PubMed1998

The erythrophore in the larval and adult dorsal skin of the brown frog, Rana ornativentris: its differentiation, migration, and pigmentary organelle formation.

To determine whether or not the erythrophore originates from xanthophores in the dorsal skin of the brown frog, Rana ornativentris, we morphologically examined the differentiation and migration of the two chromatophore types and their pigmentary organelle formation. At an early tadpole stage, three kinds of chromatophores, xanthophores, iridophores, and melanophores, appeared in the subdermis, whereas the erythrophore did so just before the foreleg protrusion stage. By the middle of metamorphosis, most chromatophores other than erythrophores had migrated to the subepidermal space. Erythrophores, which appeared late in the subdermis, proliferated actively there during metamorphosis and finished moving into the subepidermal space by the completion of metamorphosis. Carotenoid vesicles and pterinosomes within the erythrophores and xanthophores showed several significant differences in structure. In xanthophores, carotenoid vesicles were abundant throughout life, whereas those in erythrophores decreased in number with the growth of the frogs. The fibrous materials contained in the pterinosomes were initially scattered but soon formed a concentric lamellar structure. In erythrophores, the lamellar structure began to form at the periphery of the organelles but at the center in xanthophores. In addition, the pterinosomes of erythrophores were uniform in size throughout development, while those of xanthophores showed a tendency to become smaller after metamorphosis. The pterinosomes of xanthophores were significantly larger than those of erythrophores. These findings suggest that an erythrophore is not a transformed xanthophore, although they resemble each other closely in many respects.

Animals↗

PubMed2005

Pigment pattern formation in the medaka embryo.

For the study of development of pigmentation, compared with mammalian models, fish offer the advantage of multiple chromatophore types and ready access to the developing embryo for observation and experimental manipulation. Compared with zebrafish embryos, medaka embryos have an additional unique chromatophore-type and superb properties for conditional mutation studies. The rich resources of medaka mutants, combined with data obtainable from other species, potentially offer information not otherwise readily available regarding chromatophore lineage. Here we summarize the embryonic development of normal medaka pigment pattern, based on observations using embryos of a panel of wild type and mutant fish. A more detailed description of development is available in the appendix of the on-line version of this paper (see Supplementary Material). We make some comparisons with zebrafish development to emphasize the increased power of both systems when utilized together. These two models will, in combination, be a powerful system for studies of the embryogenesis and evolution of pigmentation.

Animals↗

PubMed1986

The cytomatrix regulates "resolute" transport in erythrophores.

Light microscopic studies have indicated that most microtubule-directed transport is either saltatory or resolute in nature. The latter form of transport is an intriguing phenomenon, because it commonly involves the unidirectional bulk motion of an organelle(s) such as chromosomes in dividing cells or pigment granules in chromatophores. We have investigated the ultrastructural and biochemical basis for the resolute transport of pigment in chromatophores. Light and EM studies of erythrophores in situ have clearly shown that when the microtubules were completely removed with nocodazole, resolute transport continued and was stimulated by aggregating and dispersing agents. Light and electron microscopic studies of cultured erythrophores permeabilized with digitonin indicated that resolute motion was produced by a cytomatrix of 3 to 7 nm filaments. Immunofluorescent analysis with several monoclonal antibodies raised against MAP-2 further demonstrated that MAP-2 was an important component of the contractile cytomatrix that powers pigment aggregation and dispersion. We conclude that a microtubule-associated cytomatrix normally produces resolute pigment transport in chromatophores.

Animals↗

PubMed1982

Development and growth of photosynthetic membranes of Rhodospirillum rubrum.

In cell-free extracts from low-aeration suspensions of Rhodospirillum rubrum strain G-9, bacteriochlorophyll a was distributed in two bands after rate-zone sedimentation in sucrose density gradients. From the physicochemical properties of these fractions, it was concluded that the upper band consisted of small membrane fragments, whereas the major band was composed of fragmented vesicular intracytoplasmic membrane (chromatophores). After a pulse with L-[35S]methionine, apparent polypeptide subunits of the reaction center and light-harvesting complexes within the upper pigmented fraction were labeled more rapidly than those of chromatophores; after a chase with excess unlabeled L-methionine, radioactivity from these components within the upper band appeared to be chased into the corresponding polypeptides of chromatophores. These labeling patterns are interpreted to reflect growth initiation and maturation of the photosynthetic apparatus and may, in part, represent a general mechanism for the development of vesicular intracytoplasmic membranes.

Bacterial Chromatophores↗

PubMed1984

The light-harvesting polypeptides of Rhodospirillum rubrum. II. Localisation of the amino-terminal regions of the light-harvesting polypeptides B 870-alpha and B 870-beta and the reaction-centre subunit L at the cytoplasmic side of the photosynthetic membrane of Rhodospirillum rubrum G-9+.

The unspecific proteinase K and the specific proteases alpha-chymotrypsin, trypsin and S. aureus V 8 protease were used in order to determine the orientation of the polypeptides B 870-alpha and B 870-beta from the major antenna complex B 870 of Rs. rubrum G-9+ within the chromatophore membrane (inside-out vesicle). Although B 870-alpha exhibits cleavable peptide bonds, treatment with specific proteases yielded splitting only in B 870-beta within the N-terminal region. In the case of proteinase K, which was most effective, mainly 6 (B 870-alpha) and 16 (B 870-beta) amino acid residues were removed from their N-terminal parts as proved by means of Edman degradation of cleavage products. The major peptide bonds cleaved were identified as Gln6-Leu7 in B 870-alpha and as Lys16-Glu17 in B 870-beta. The central hydrophobic stretch regions and the relatively hydrophilic C-terminal parts of both light-harvesting polypeptides were not affected by proteinase K. On the basis of these degradation experiments a transmembrane orientation of B 870-alpha and B 870-beta is postulated, with their N-terminal towards the cytoplasm and their C-termini towards periplasm with regard to the photosynthetic membrane. This hypothesis is supported by the transmembrane model proposed by Brunisholz et al. (Hoppe-Seyler's Z., Physiol. Chem., (1984) 365, 675-688) in which the hydrophobic stretch of B 870-alpha and of B 870-beta forming an alpha-helix would span the membrane once. Organic solvent extraction of chromatophores treated with proteinase K yielded a fairly pure polypeptide fragment with an apparent molecular mass of 14000 Da. Its N-terminal amino-acid sequence is identical with the sequence within the N-terminal region of the reaction centre subunit L of Rs. rubrum G-9+. Thus it is most likely that as in the case of B 870-beta, proteinase K removed 16 amino acid residues from the N-terminal part of subunit L. This subunit therefore also seems to be exposed at the surface of the cytoplasmic side of the chromatophore membrane.

Amino Acids↗

PubMed1979

[Electronmicroscopic studies on the skin pigmentation of the red bellied toad Bombina bombina (L.)].

The various colours of the red-bellied toad Bombina bombina are caused by 3 types of chromatophores, the red xanthophores, the white iridophores and the black melanophores. In the brownish skin and in the black spots of the dorsal region all types of chromatophores are found. But in the epidermis of the black spots there are more grana of melanin than in the other region of the back. The 3 types of chromatophores are not present in the skin of all parts of the body. The dark blue colour of the belly is caused only by melanophores, whereas in the ventral parts with light blue colour there occur melanophores and iridophores. The white spots of the belly contain only iridophores, the red spots have iridophores and xanthophores.

Animals↗

PubMed1977

[Isolation and characterization of pigment-protein complexes from green serobacteria Chlorobium limicola forma thiosulfatophilum].

A subchromatophore fraction containing the reaction center P-840 was isolated from the chromatophores of green serobacteria Chlorobium limicola forma thiosulfatophilum by ultracentrifugation and its protein composition was characterized. After treatment of the chromatophores by Triton X-100 and subsequent polyacrylamide gel electrophoresis two pigment-protein complex containing bacterioviridin. The proteins of the pigment-protein complex containing bacterioviridin. The proteins of the pigment-protein complexes were obtained. The first complex contained mainly bacteriochlorophyll alpha with bacterioviridin contaminations and the second one-only bacterioviridin. The low-temperature absorption spectrum of the bacteriochlorophyll alpha-containing pigment-protein complex is identical to the absorption spectrum of a water-soluble pigment-protein complex isolated and characterized by Olson and contains proteins with molecular weights of 34.800, 33.100, 27.500 and 23.200. A protein with molecular weight of 32.700 was found in the pigment-protein complexes were compared to the proteins of the photochemically active subchromatophore fraction and chromatophores.

Bacterial Chromatophores↗

PubMed1997

Malignant chromatophoroma in a canebrake rattlesnake (Crotalus horridus atricaudatus).

An adult female canebrake rattlesnake (Crotalus horridus atricaudatus) at Zoo Atlanta (Atlanta, Georgia, USA) had a subcutaneous mass on the left lateral abdomen. Microscopically, the tumor contained a pleomorphic population of cells with abundant intracytoplasmic brown to gold nonrefractile pigment (chromatophores), large stellate cells resembling neurons, and small stellate cells whose cytoplasmic processes formed a fibrillar matrix. The pigment stained black with the Fontana-Masson technique and was positive with the periodic acid-Schiff technique (prior to and after diastase treatment). Neuron-specific enolase was detected in the large stellate cells using an immunohistochemical staining technique. In addition, glial fibrillary acidic and S-100 proteins were detected in the chromatophores with immunohistochemical staining. The smaller stellate cells were strongly S-100 positive. Ultrastructurally, chromatophores contained intracytoplasmic structures composed of concentric lamellar membranes bordered by a triple-layer outer membrane. The morphology of these structures was compatible with pterinosomes. Three fluorescent pigments were isolated from the neoplasm by one-dimensional chromatography and characterized by spectrophotometry and spectrofluorometry.

Animals↗