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At least 19 recordsLinked to original sources
PubMed1978

Proteins exposed at the surface of chromatophores of Rhodospirillum rubrum: the orientation of isolated chromatophores.

The exposure of proteins at the surface of isolated chromatophores (i.e., the cytoplasmic face of intracytoplasmic membranes) of Rhodospirillum rubrum was studied by proteolysis as well as by enzymatic iodination with 125I. Analyses were performed after polyacrylamide gel electrophoresis of chromatophore proteins solubilized with sodium dodecyl sulfate. Reversible light induced proton uptake by partially digested chromatophores was used as a criterion for the integrity of the permeability barrier and thus, as evidence for proteolysis only of proteins outside of this barrier. Trypsin or alpha-chymotrypsin completely cleaved four proteins which were identified as the heavy subunit of succinate dehydrogenase (Mr = 64 000), the alpha- and beta-subunits of coupling factor ATPase (Mr = 55 000 and 51 000), and the heavy (H) subunit of photochemical reaction centers (Mr = 31 000). alpha-Chymotrypsin, in addition, attacked the protein (Mr = 9000) of light harvesting bacteriochlorophyll preparations. By enzymatic iodination, the same proteins were labeled as were digested with trypsin or alpha-chymotrypsin except for the protein of Mr = 9000. In addition, significant label was incorporated into three more proteins, one of which (Mr = 41 000) could be identified as a major protein of the cell wall. The complete cleavage with trypsin of four proteins exposed at the surface indicated that isolated chromatophores were homogeneously oriented regardless of the method employed for cell breakage, i.e., passage through a French pressure cell at different forces or osmotic shock of sphaeroplasts.

Bacterial Chromatophores↗
PubMed1991

Localization of chromatophore proteins of Rhodobacter sphaeroides. I. Rapid Ca(2+)-induced fusion of chromatophores with phosphatidylglycerol liposomes for proteinase delivery to the luminal membrane surface.

A protease delivery system was developed for the exclusive and controlled digestion of proteins exposed at the morphological inside (periplasmic surface) of Rhodobacter sphaeroides chromatophores. In this procedure, proteinase K is encapsulated within large unilamellar liposomes which are fused to the chromatophores in the presence of Ca2+ ions. The liposomes were prepared by a detergent dialysis procedure from native phosphatidylglycerol and found to undergo rapid bilayer fusion with purified chromatophore preparations above a threshold concentration of 12.5 mM CaCl2. The fusion process was complete within 10 min at 35 mM Ca2+ with about 80% of the pigment located in the fusion products. Electron micrographs of freeze-fracture replicas confirmed the intermixing of the lipid bilayers and the unilamellar structure of the fused membrane vesicles. The procedure did not affect the labile B800 chromophore of the B800-850 antenna complex, but reduced slightly the absorption due to the B875 core antenna. Emission from both light-harvesting complexes was increased in the fused membranes, suggesting a partial dissociation of photosynthetic units in the expanded bilayer. The results, together with those presented in the following paper (Theiler, R., and Niederman, R. A. (1991) J. Biol. Chem. 266, 23163-23168), demonstrate that this new method fulfills the stringent requirements for a successful delivery of macromolecules to the chromatophore interior.

Bacterial Chromatophores↗
PubMed1981

X-ray diffraction studies on chromatophore membrane from photosynthetic bacteria. I. Diffraction pattern of the photoreaction unit isolated from Rhodospirillum rubrum chromatophore and some characteristics of the structure.

The X-ray diffraction pattern from chromatophore membranes of a photosynthetic bacterium, Rhodospirillum rubrum, indicates that a highly organized protein assembly exists in the membrane. The X-ray scatterer was solubilized from chromatophores by a mixture of cholate and deoxycholate. The basic component was identified as the photoreaction unit, which consists of light-harvesting bacteriochlorophyll proteins and a reaction center. The radial autocorrelation function, calculated directly from the X-ray intensity dats, made it possible to deduce certain structural features of the X-ray scatterer. 1. The maximum dimension of the X-ray scatterer is estimated to be 110-130 A. 2. The arrangement of the units in the chromatophore membrane is random. 3. Protein molecules in the unit form a rigid structure, being arranged mutually in fixed positions to give a distinct X-ray diffraction pattern. 4. The most probable structure is one which has rotational symmetry.

Bacterial Chromatophores↗
PubMed2001

Cephalopod chromatophores: neurobiology and natural history.

The chromatophores of cephalopods differ fundamentally from those of other animals: they are neuromuscular organs rather than cells and are not controlled hormonally. They constitute a unique motor system that operates upon the environment without applying any force to it. Each chromatophore organ comprises an elastic sacculus containing pigment, to which is attached a set of obliquely striated radial muscles, each with its nerves and glia. When excited the muscles contract, expanding the chromatophore; when they relax, energy stored in the elastic sacculus retracts it. The physiology and pharmacology of the chromatophore nerves and muscles of loliginid squids are discussed in detail. Attention is drawn to the multiple innervation of dorsal mantle chromatophores, of crucial importance in pattern generation. The size and density of the chromatophores varies according to habit and lifestyle. Differently coloured chromatophores are distributed precisely with respect to each other, and to reflecting structures beneath them. Some of the rules for establishing this exact arrangement have been elucidated by ontogenetic studies. The chromatophores are not innervated uniformly: specific nerve fibres innervate groups of chromatophores within the fixed, morphological array, producing 'physiological units' expressed as visible 'chromatomotor fields'. The chromatophores are controlled by a set of lobes in the brain organized hierarchically. At the highest level, the optic lobes, acting largely on visual information, select specific motor programmes (i.e. body patterns); at the lowest level, motoneurons in the chromatophore lobes execute the programmes, their activity or inactivity producing the patterning seen in the skin. In Octopus vulgaris there are over half a million neurons in the chromatophore lobes, and receptors for all the classical neurotransmitters are present, different transmitters being used to activate (or inhibit) the different colour classes of chromatophore motoneurons. A detailed understanding of the way in which the brain controls body patterning still eludes us: the entire system apparently operates without feedback, visual or proprioceptive. The gross appearance of a cephalopod is termed its body pattern. This comprises a number of components, made up of several units, which in turn contains many elements: the chromatophores themselves and also reflecting cells and skin muscles. Neural control of the chromatophores enables a cephalopod to change its appearance almost instantaneously, a key feature in some escape behaviours and during agonistic signalling. Equally important, it also enables them to generate the discrete patterns so essential for camouflage or for signalling. The primary function of the chromatophores is camouflage. They are used to match the brightness of the background and to produce components that help the animal achieve general resemblance to the substrate or break up the body's outline. Because the chromatophores are neurally controlled an individual can, at any moment, select and exhibit one particular body pattern out of many. Such rapid neural polymorphism ('polyphenism') may hinder search-image formation by predators. Another function of the chromatophores is communication. Intraspecific signalling is well documented in several inshore species, and interspecific signalling, using ancient, highly conserved patterns, is also widespread. Neurally controlled chromatophores lend themselves supremely well to communication, allowing rapid, finely graded and bilateral signalling.

Animals↗
PubMed2000

Roles of glutamate and FMRFamide-related peptides at the chromatophore neuromuscular junction in the cuttlefish, Sepia officinalis.

Body patterning behavior, the expression of highly intricate patterns, is ubiquitous among all unshelled cephalopods. These body patterns are in part generated by the coordinated activity of millions of skin chromatophore organs, each of which is regulated by a set of chromatophore muscles directly innervated by centrally located chromatophore motoneurons. This study addresses the question of the identity and function of the transmitter(s) at the chromatophore neuromuscular junction (NMJ) in the European cuttlefish Sepia officinalis. Glutamate application causes a rapid contraction of the chromatophore muscles, resulting in chromatophore expansion. Pharmacological studies demonstrate that the chromatophore muscles contain receptors blocked by glutamate-specific antagonists. Glutamate-like immunoreactivity is also present in the somata of putative chromatophore motoneurons. These findings suggest that glutamate likely acts as a neurotransmitter at the chromatophore NMJ. Evidence is also presented suggesting that FMRFamide-related peptides (FaRPs) also function as neurotransmitters at the Sepia chromatophore NMJ. FMRFamide application causes contraction of chromatophore muscles; however, the FMRFamide effect is slower and longer lasting than that of glutamate. Pharmacological data show that FMRFamide acts directly on the chromatophore muscles. FMRFamide-immunopositive cells are present in the posterior chromatophore lobe, the putative location of the chromatophore motoneuron somata. A combination of immunocytochemistry and in situ hybridization shows that some putative chromatophore motoneurons express FaRP-like immunoreactivity and an FaRP-coding mRNA transcript. Many FMRFamide-immunopositive cells in the posterior chromatophore lobes also express glutamate-like immunoreactivity. We conclude that glutamate and FaRPs likely function as fast and slow transmitters, respectively, at the Sepia chromatophore NMJ.

Animals↗
PubMed1996

Peptidergic regulation of chromatophore function in the European cuttlefish Sepia officinalis

Color patterning in cephalopod molluscs involves activation of a peripheral chromatophore system that is under neuromuscular control. The complex behavior of individual chromatophores is mediated by a specific set of muscles, the chromatophore muscles, that receive direct innervation from the central nervous system. To date, glutamate is the only excitatory transmitter that has been proposed to act at the chromatophore neuromuscular junction of cephalopods. We present data demonstrating that the chromatophore muscles in the European cuttlefish Sepia officinalis are also regulated by the FMRFamide family of neuropeptides. Using an in vitro chromatophore bioassay, it has been determined that several FMRFamide-related peptides (FaRPs) are potent excitors of the chromatophore muscles, causing chromatophore expansion. Immunocytochemical analyses of the central nervous system using an FMRFamide antibody revealed the presence of FMRFamide-like immunoreactive cell bodies in the posterior chromatophore lobes, the region of the brain containing the chromatophore motoneurons of the fin and mantle. FMRFamide-like immunoreactivity was also seen in the periphery, in the nerves around the chromatophores and in close apposition to the muscles in the chromatophore layer of the fin. HPLC analysis of the fin dermis isolated four bioactive peaks that were FMRFamide-immunoreactive when tested on an immunoblot assay. Two of these peaks co-eluted with known FaRPs, FMRFamide and ALSGDAFLRFamide, a decapeptide isolated from squid. Taken together, these data suggest that the FaRPs are likely to be endogenous excitors of the chromatophore muscles in cephalopods.

Journal Article↗
PubMed1986

Chromatophore motoneurons in the brain of the squid, Lolliguncula brevis: an HRP study.

The location of the motoneuron somata controlling activity of the chromatophore muscles was studied in the squid Lolliguncula brevis. Retrograde transport of horseradish peroxidase from injection sites in the skin or in the mantle muscle established that the chromatophore motoneurons are situated in the subesophageal mass of the brain while at least some of the mantle muscle motoneurons are in the stellate ganglia. Motoneurons to chromatophores in the mantle have their somata in the posterior subesophageal mass, mainly in the chromatophore or fin lobes. Motoneurons to chromatophores in the head are located in the anterior pedal lobes and those to the chromatophores in the arms project mainly from the anterior chromatophore lobes. However, some neurons in the posterior chromatophore lobes project to the head or arm regions. A few cells in both the anterior and posterior chromatophore lobes project contralaterally. Somata in other lobes of the subesophageal mass are also labelled by injections in the skin or in the mantle muscle. Evidence presented here suggests that some of the neurons labelled outside the chromatophore lobes are chromatophore motoneurons.

Animals↗
PubMed1983

The interaction of 4-chloro-7-nitrobenzofurazan with Rhodospirillum rubrum chromatophores, their soluble F1-ATPase, and the isolated purified beta-subunit.

ATP synthesis and hydrolysis by Rhodospirillum rubrum chromatophores as well as the soluble RrF1-ATPase activity are inhibited by 4-chloro-7-nitrobenzofurazan (NBD-C1) in a dithiothreitol-reversible manner. Using the method earlier developed in these chromatophores to remove specifically the beta-subunit from their membrane-bound RrF1 leaving all other subunits attached to the resulting inactive beta-less chromatophores (Philosoph, S., Binder, A., and Gromet-Elhanan, Z. (1977) J. Biol. Chem. 252, 8747-8752), we have tested the effect of NBD-Cl also on the isolated beta-subunit and on the beta-less chromatophores before and after their reconstitution with the missing beta-subunit. The isolated purified beta-subunit as well as the RrF1-ATPase bind covalently [14C]NBD-Cl with an accompanying increase in absorbance at 385 nm, indicative of a tyrosyl-O-NBD bond. But, unlike the inactive RrF1-NBD complex, the beta-NBD adduct is as capable as the native beta-subunit to reconstitute beta-less chromatophores and restore their ATP synthesis and hydrolysis activities. On the other hand, incubation of beta-less chromatophores with NBD-Cl before or after their reconstitution with either native beta or the NBD-saturated beta adduct results in complete inhibition of their restored activities. It is, therefore, concluded that there are different binding sites for NBD-Cl on the isolated beta-subunit and on the beta-less chromatophores or on chromatophores reconstituted with the beta-NBD adduct, where the beta-site is already occupied. Furthermore, the site responsible for inactivation by NBD-Cl of the coupled and reconstituted chromatophores and of the soluble RrF1 is different from the site modified by NBD-Cl on the isolated beta-subunit. Its subunit location is as yet unknown.

4-Chloro-7-nitrobenzofurazan↗
PubMed1999

Retinoic acid stimulates development of adult-type chromatophores in the flounder.

Premetamorphic flounder larvae were administered different doses of 9-cis retinoic acid (9cRA). 9cRA at 25 nM (the highest dose) not only stimulated adult-type (ad-) chromatophore development on the ocular (eyed) side, but also induced the development of ad-chromatophores on the blind (non-eyed) side of the metamorphosed fish. The ad-chromatophore development was stimulated by 9cRA only when administered to the larvae that were at late premetamorphosis and at early prometamorphosis. Ad-chromatophores actually appear much later, at the end of metamorphosis. 9cRA was not effective at later stages of metamorphosis. These results suggest that 9cRA stimulated the development or determination of the developmental fate of neural crest cells for chromatophores. The present results also suggest the presence of immature chromatophores or neural crest cells on both sides of the larval body of the flounder and that the ad-chromatophore development is somehow inhibited on the blind side in spontaneous metamorphosis. All-trans retinoic acid (atRA) had a similar effect on the ad-chromatophore development. In addition, both types of RAs affected the development of fin rays of the fish, resulting in deformity of fins when administered at high doses early in metamorphosis. The teratogenic effect of atRA was greater than that of 9cRA.

Alitretinoin↗
PubMed1999

The structure of chromatophores from purple photosynthetic bacteria fused with lipid-impregnated collodion films determined by near-field scanning optical microscopy.

Lipid-impregnated collodion (nitrocellulose) films have been frequently used as a fusion substrate in the measurement and analysis of electrogenic activity in biological membranes and proteoliposomes. While the method of fusion of biological membranes or proteoliposomes with such films has found a wide application, little is known about the structures formed after the fusion. Yet, knowledge of this structure is important for the interpretation of the measured electric potential. To characterize structures formed after fusion of membrane vesicles (chromatophores) from the purple bacterium Rhodobacter sphaeroides with lipid-impregnated collodion films, we used near-field scanning optical microscopy. It is shown here that structures formed from chromatophores on the collodion film can be distinguished from the lipid-impregnated background by measuring the fluorescence originating either from endogenous fluorophores of the chromatophores or from fluorescent dyes trapped inside the chromatophores. The structures formed after fusion of chromatophores to the collodion film look like isolated (or sometimes aggregated, depending on the conditions) blisters, with diameters ranging from 0.3 to 10 microm (average approximately 1 microm) and heights from 0.01 to 1 microm (average approximately 0.03 microm). These large sizes indicate that the blisters are formed by the fusion of many chromatophores. Results with dyes trapped inside chromatophores reveal that chromatophores fused with lipid-impregnated films retain a distinct internal water phase.

Bacterial Chromatophores↗
PubMed2002

Fish chromatophores as cytosensors in a microscale device: detection of environmental toxins and bacterial pathogens.

Fish chromatophores from Betta splendens are used as the cytosensor element in the development of a portable microscale device capable of detecting certain environmental toxins and bacterial pathogens by monitoring changes in pigment granule distribution. The adaptation of chromatophores to a microscale environment has required the development of enabling technologies to produce miniaturized culture chambers, to integrate microfluidics for sample delivery, to miniaturize image capture, and to design new statistical methods for image analyses. Betta splendens chromatophores were selected as the cytosensor element because of their moderate size, their toleration of close contact, and most importantly, for their responses to a broad range of chemicals and pathogenic bacteria. A miniaturized culture chamber has been designed that supports chromatophore viability for as long as 3 months, and that can be easily transported without damage to the cells. New statistical methods for image analyses have been developed that increase sensitivity and also decrease the time required for detection of significant changes in pigment granule distribution. Betta chromatophores have been tested for their responses to selected pathogenic bacteria and chemical agents. We discuss in detail the aggregation of pigment granules seen when chromatophores are incubated with Bacillus cereus, a common cause of food poisoning. Also described are the more subtle responses of chromatophores to a class of environmental chemical toxins, polynuclear aromatic hydrocarbons. We show that the chromatophores are able to detect the presence of certain polynuclear aromatic hydrocarbons at concentrations lower than the Environment Protection Agency (EPA) 550.1 standards.

Animals↗
PubMed1976

Membranes of Rhodospirillum rubrum: physicochemical properties of chromatophore fractions isolated from osmotically and mechanically disrupted cells.

Isolation of highly purified membrane fractions from phototrophically grown Rhodospirillum rubrum was achieved by velocity and isopyknic sedimentation under carefully controlled ionic conditions. Bacteriochlorophyll-rich and succinic dehydrogenase-rich chromatophores that were essentially devoid of contamination by non-chromatophore protein were separated from a denser fraction in extracts disrupted in a French pressure cell. Highly purified chromatophores and a nearly photopigment-free envelope fraction were also obtained from cells lysed by treatment with ethylenediaminetetraacetate-lysozyme-Brij 58. After lysis with lysozyme and ethylenediaminetetraacetate alone, about 50% of the total photosynthetic pigment was released in chromatophores similar to those isolated by the above procedures. Chromatophores prepared by each method were found to have very similar near-infrared absorption spectra, overall chemical composition, equilibrium buoyant densities in CsCl, and protein patterns in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The protein profiles of the dense, outer membrane-rich fractions were different from those of the chromatophores. The release of much of the photosynthetic apparatus as discrete chromatophores is osmotically lysed extracts necessitates a reevaluation of the concept that isolated chromatophores arise only from mechanical comminution of a larger membrane structure.

Bacterial Chromatophores↗
PubMed1992

Pteridines in the yellow-colored chromatophores of the isopod, Armadillidium vulgare.

Biochemical analyses of the dorsal integument of the isopod, Armadillidium vulgare, revealed that sepiapterin, biopterin, pterin, isoxanthopterin and uric acid accumulated in the yellow-colored chromatophores which are distinguishable from ommochrome chromatophores. The pattern of the yellow-colored chromatophores in the female is externally observable at the dorsal surface of the integument as yellow markings. In contrast, the yellow-colored chromatophores are not externally observable in the male, since they are covered by an ommochrome chromatophore layer. The content of both sepiapterin and biopterin in the male chromatophores was about two times greater than that in the female. The yellow-colored chromatophores were observable by light microscopy as pigmented granules. Electron microscopy showed that morphological properties of the granules were similar to those of pteridine granules which contain uric acid occurring in the silkworm integument. These facts indicate that both pteridines and uric acid in the integument of A. vulgare are localized in the pigmented granules of the yellow-colored chromatophores.

Animals↗
PubMed1991

Localization of chromatophore proteins of Rhodobacter sphaeroides. II. Topography of cytochrome c1 and the Rieske iron-sulfur protein as determined by proteolytic digestion of the outer and luminal membrane surfaces.

Proteinase K was used to degrade membrane proteins exposed at the outer (cytoplasmic) and inner (periplasmic) surface of sealed, uniformly oriented chromatophore vesicles of Rhodobacter sphaeroides. Exclusive and controlled digestion of the chromatophore interior was achieved after Ca(2+)-induced fusion with large unilamellar phosphatidylglycerol liposomes containing microencapsulated enzyme. Reaction center subunit H, which served as a marker for the outer surface, was degraded to a slightly smaller product in chromatophores. This protein remained intact after liposome-chromatophore fusion, suggesting that the intermixing of lipid bilayers proceeded without significant leakage of the aqueous vesicle contents. In contrast, while cytochrome c1 was not affected in chromatophores, 70-75% was degraded within 60 min after liposome-chromatophore fusion. These results support an arrangement in which the bulk of this protein, including the mesoheme component and active site residues, faces the periplasmic side of the membrane. Although current functional models for the cytochrome bc1 complex predict that the Rieske iron-sulfur center interacts with cytochrome c1 in the periplasm, the iron-sulfur protein resisted proteolytic attack in the liposome-chromatophore fusion products under conditions that caused extensive degradation of cytochrome c1. Two cleavage products of the iron-sulfur protein were observed after the digestion of chromatophores, suggesting both a heterogeneity in the population of this protein and the exposure of at least part of its molecular mass to the cytoplasm.

Bacterial Chromatophores↗
PubMed1975

Role of ubiquinone-10 in electron transport system of chromatophores from Rhodospirillum rubrum.

The role of ubiquinone-10 in the activities for the reduction of free cytochrome c2 and bound cytochrome cc' by succinate was studied with chromatophores from a blue-green mutant (G-9) of Rhodospirillum rubrum. 1. By a single extraction with isooctane, approximately 90% of ubiquinone-10 was easily removed from the chromatophores. In the extracted chromatophores, the activity for succinate-cytochrome c2 reduction decreased to 5-10% of the original activity. This depressed activity was mostly restored by adding ubiquinone-10. The remaining quinone was hardly extractable, even by repeated extractions. With repeatedly extracted chromatophores, the activity for succinate-cytochrome c2 reduction was mostly restored to the same extent as with once-extracted chromatophores, whereas the extent of inhibtion of the activity by antimycin A gradually fell. 2. In isooctane-extracted chromatophores, the activity for the reduction of bound cytochrome cc' by succinate under anaerobic conditions decreased to 35 to 95% of the original level. With chromatophores in which the remaining activity was as low as 40% of the original level, the activity was partially restored by adding ubiquinone-10, but this was not the case with chromatophores in which the remaining activity was higher than approximately 50% of the original level.

Alkanes↗