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PubMed1987

Bacterial membrane proteins.

Bacterial membranes have diverse functions, depending on whether they are specialized membranes or cytoplasmic membranes possessing transport, mitochondrial activities and biosynthetic functions for assembly of membranes, walls and capsules. In contrast to plasma membranes which serve as major biochemical organelles of both Gram-positive and Gram-negative bacteria, the outer membranes of the latter group confer barrier functions on the cells, providing a variety of selective channels. Although prokaryotic cells lack the array of membranous organelles characteristic of eukaryotic cells, bacteria with specific physiological and genetic capabilities form specialized membrane systems such as the bacteriorhodopsin purple membrane, chromatophore membranes of phototrophs, and forespore membranes essential to bacterial endospore formation. Unravelling the structure, function and proteins of these membranes presents a formidable biochemical, immunochemical and structural challenge.

Bacterial Outer Membrane Proteins↗
PubMed1987

Primary structure of an analog of crustacean pigment-dispersing hormone from the lubber grasshopper Romalea microptera.

An octadecapeptide capable of inducing pigment dispersion in the chromatophores of the fiddler crab Uca pugilator has been isolated from lyophilized heads of the lubber grasshopper Romalea microptera. This pigment-dispersing factor (PDF) was purified by gel filtration, ion-exchange chromatography, partition chromatography, and reversed-phase high performance liquid chromatography. Automated gas-phase sequencing, followed by the identification of the carboxyl-terminal amide, established the primary structure of this PDF as Asn-Ser-Glu-Ile-Ile-Asn-Ser-Leu-Leu-Gly-Leu-Pro-Lys-Leu-Leu-Asn-Asp-Ala- NH2. This structure was confirmed by chemical synthesis and by demonstrating that the synthetic and native PDF displayed identical chromatographic behavior and biological activity. The Romalea PDF is structurally related to the crustacean pigment-dispersing hormones (PDHs), which are also octadecapeptides. The sequence of grasshopper PDF shows 78% homology with beta-PDH (from the crabs U. pugilator and Cancer magister) and 50% homology with alpha-PDH (from the prawn Pandalus borealis). This study provides the first direct chemical evidence for the structural relatedness of insect PDF to the crustacean PDHs, thus identifying them as an authentic family of arthropod peptides.

Amino Acid Sequence↗
PubMed1985

Topology and neighbor analysis of the photosynthetic reaction center from Rhodopseudomonas sphaeroides.

The subunit arrangement of the reaction center complex (RC) of Rhodopseudomonas sphaeroides was studied by chemical modification with four different cross-linking reagents using purified RC in lauryldimethylamine oxide, RC incorporated into liposomes, and intact chromatophore membranes, from which RCs are isolated. The RC of R. sphaeroides is composed of three polypeptide subunits, H, M, and L, apparent molecular mass as determined in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, of 28,000, 24,000, and 21,000, respectively. The intra-complex products produced, were found to contain the polypeptides H-M-L, H-M, H-L, and M-L linked together. In addition, the cross-linking of cytochrome c to solubilized and membrane-bound RCs was observed with all four reagents. The products were found to be only a cytochrome c linked to either the M or L polypeptide. These results indicate that a portion of the L and M subunits of the RC must be exposed in situ on the periplasmic surface of the membrane near a binding site for cytochrome c on the RC, and all three subunits must be in close proximity to one another.

Chlorophyll↗
PubMed1985

Microtubule--and microfilament--disrupting drugs and melanosome migration in melanophores of Papiliochromis ramirezi (Cichlidae, Teleostei).

We report here the effects of cytochalasin B, colchicine and vinblastine on melanosome migration in Papiliochromis ramirezi melanophores. Melanosome migration was not affected by 2 X 10(-5) M cytochalasin B. On the other hand, the aggregation, usually elicited by 10(-6) M norepinephrine, was completely inhibited by simultaneous treatment with 10(-3) M colchicine and cold (0-3 degrees C). Same results were obtained with 10(-3) M vinblastine. Lower concentrations of colchicine had no effect on granule aggregation. However, the aggregation in 50% of the melanophores was still blocked by 10(-5) M vinblastine, whereas 10(-7) M vinblastine was ineffective. Melanosome dispersion usually elicited by 10(-3) M theophylline was significantly accelerated by 10(-3) M colchicine, but delayed by 10(-3) M vinblastine. Lower concentrations of both agents had no effect on pigment dispersion. Therefore our results strongly suggest that microtubule structural integrity is essential to P. ramirezi melanosome displacements. As cytochalasin B had no effect on pigment migration, actin-like microfilaments might be either non-related to granule motion or absent in these chromatophores.

Actin Cytoskeleton↗
PubMedDate not supplied

[Relationship between the electron structure of phosphates and the problem of ATP synthesis and utilization].

The nature of macroergic bonds and some problems of ATP formation and utilization are considered in terms of electron structure of phosphates. The main acting compound in the ATP synthesis and in the reactions of transfer and utilization of the energy of macroergic bonds as well, is ATP terminal phosphate or phosphoryl group which in the free state is a monomeric methaphosphate-ion. High reactive ability of monomeric methaphosphate-ion, its affinity of lown electrom pairs is conditioned by the presence of a vacant sp3-orbitals in phosphor atom of methaphosphate-ion. Therefore in the reactions with ATP participation the phosphoryl group plays the role of electrophilic agent. Formation of intermediate methaphosphate-ion preceding the synthesis of ATP from ADP during substrate phosphorylation results from the breakage of O--P bond, during which both electrons which form the bond stay in the oxygen atom. Another possible pathway of methaphosphate-ion formation is the ejaction of the electron from ortophosphate dianion with the help of suitable acceptor of the electrons, by light-stimulated pigment system of chloroplasts or chromatophores or singlet oxygen liberated during the decomposition of hydrogen peroxide with catalase. Due to the redistribution of electron density in the phosphate radical the latter turns into the monomeric methaphosphate-ion bound to ADP with the formation of ATP.

Adenosine Triphosphate↗
PubMedDate not supplied

Ecology of Zygnema stellinum Vauch. during desiccation of a shallow body of water.

the effect of desiccation on the green alga Zygnema, a typical aquatic form of the order Conjugatae, family Zygnemaceae, is investigated. The vegetative reproduction of Zygnema occurs with the separation of the filaments in two different ways. It is shown that changes take place in cell morphology during desiccation. After division most of the cells acquire the shape of a square. These are usually half as large as the vegetative cells prior to division. Also, the form and color of the chromatophores change; they become green-brown, i.e., Zygnema falls into a state of rest, since no cell division is observed. During this state of rest the filaments suffer the unfavorable conditions of summer drought. In the fall, at the end of August, with the shortening of the day and reduction of temperature, the alga develops parthenospores for overwintering.

Chlorophyta↗
PubMedDate not supplied

[Isotope effects on electron tunneling reactions in biological systems conformational mobility of proteins].

Effects of D2O substitution on electron transport reactions in proteins were analysed on the basis of generally adopted ideas of electronic vibration interactions and conformational mobility of macromolecules. At the molecular level, a mechanism for cytochrome c oxidation was established. On the basis of general viscosity and elasticity properties of proteins, the effects of temperature and chemical composition of the medium on conformational relaxation were analysed. For chromatophores of photosynthetising bacteria, a mechanism is discussed by which abnormal effects of temperature and abnormal isotope effects may be exercised on charge recombination.

Cytochrome c Group↗
PubMedDate not supplied

[Electron-conformation transitions in the complex of bacterial photosynthetic reaction centers with cytochromes].

A theoretical model of conformation--regulated electron transfer from multihaem cytochrome c to bacteriochlorophyll of the reaction centre (RC) is considered. The theoretical data are compared with the experimental ones on the basis of temperature dependence of laser-induced electron transfer from high-potential cytochrome Ch bacheriochlorophyll of RC in Ectothiohodospira shaposhnikovii chromatophores. From this comparison there were calculated the thermodynamic characteristics of cytochrome Ch transfer from the configuration without electron transfer to RC bacteriochlorophyll into the coordinated configuration with an effective transfer. The values obtained are: H = 7,1 kJ/M; S = --(30,2--36,9) J/grad. M. Possible regulatory role of such conformation transitions is discussed.

Bacterial Proteins↗
PubMed1984

Localization of phospholipid biosynthetic enzyme activities in cell-free fractions derived from Rhodopseudomonas sphaeroides.

The phospholipid biosynthetic enzyme activities: CDP-diglyceride synthetase, phosphatidylglycerophosphate synthetase, PGP phosphatase, phosphatidylserine (PS) synthase, PS decarboxylase, and S-adenosyl-L-methionine:phosphatidylethanolamine (AdoMet:PE) N-methyltransferase were detected in crude cell-free extracts of Rhodopseudomonas sphaeroides. CDP-diglyceride synthetase and phosphatidylglycerophosphate synthetase co-enriched with penicillin-binding protein activity, a known cytoplasmic membrane marker, throughout fractionation of cell-free extracts of both chemoheterotrophically and photoheterotrophically grown cells. PS decarboxylase also co-enriched with the cytoplasmic membranes in fractions derived from chemoheterotrophically and photoheterotrophically grown cells, but substantially greater quantities of PS decarboxylase activity was found in the chromatophores derived from photoheterotrophically grown cells than could be accounted for by cytoplasmic membrane contamination of this sample. PS synthase (60% of the recovered activity) and S-adenosyl-L-methionine:phosphatidylethanolamine N-methyltransferase (90% of the recovered activity) were found in the supernatant fraction after high speed centrifugation of crude cell lysates, suggesting that these enzyme activities were not tightly membrane associated. The localization of phospholipid biosynthetic enzyme activity in R. sphaeroides is discussed in terms of the biosynthesis of the photosynthetic membranes.

CDPdiacylglycerol-Serine O-Phosphatidyltransferase↗
PubMed1984

Correlation of epizootiological observations with experimental data: chemical induction of chromatophoromas in the croaker, Nibea mitsukurii.

Chromatophoromas in the croaker nibe, Nibea mitsukurii, are common neoplasms in feral fish which inhabit the shallow water in a unique geographic distribution along the Pacific coast of Japan. We undertook surveys of the epizootiology of tumor-bearing fish at 25 sites. The highest tumor incidence occurred at the station near the mouth of the Kumano river and was 47% (1,415 of 2,991). The incidence at 2 adjacent survey stations located approximately 18 and 30 km away were 2.7 and 2.5%, respectively. At the other survey stations, no tumor incidences were recorded or they were less than 5%. During the course of experimental studies on the chromatophoromas using tank-reared nibe, we found that nifurpirinol (NP), a drug used for the treatment of fish diseases, might also induce the chromatophoromas in the fish, as well as N-methyl-N'-nitro-N-nitrosoguanidine and 7,12-dimethylbenz[alpha]anthracene. Therefore, tank-reared nibe 5 months of age were divided into 4 groups of about 50 each and exposed to water containing 0, 0.5, 1, or 2 ppm NP, respectively, fourteen times for 1 hour each time. Three hundred nibe were kept as untreated controls. The incidences of chromatophore hyperplasia or neoplasia per group at 13 months were as follows: the untreated: 2.9% (6 of 204), 0 ppm: 5.3% (2 of 38), 0.5 ppm: 73% (36 of 49), 1 ppm: 87% (20 of 23), and 2 ppm: 100% (2 of 2). These and other results led us to believe that 1) NP is a carcinogen, 2) nibe have a high susceptibility to induction of chromatophoromas by chemical carcinogens, and 3) some environmental chemicals are causal factors in the hyperendemic occurrences of the tumors in wild nibe.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1984

Purification and properties of the activating enzyme for iron protein of nitrogenase from the photosynthetic bacterium Rhodospirillum rubrum.

The oxygen-labile, activating enzyme for iron protein from the photosynthetic bacterium, Rhodospirillum rubrum, was purified 11,800-fold using a combination of chromatophore washing, DE52-cellulose chromatography, hydroxylapatite chromatography, reactive red-120 cross-linked agarose chromatography, reactive red-120 cross-linked agarose chromatography, and Sephadex G-75 gel filtration. Activating enzyme appeared homogeneous on silver-stained sodium dodecyl sulfate-polyacrylamide gels, and the staining intensity of the activating-enzyme band was correlated with the activating-enzyme activity observed in in vitro assays. Either formaldehyde fixation or higher acrylamide concentration was required to accurately assess the purity of activating enzyme on silver-stained gels. Activating enzyme was stable for 30 days at 4 degrees C. Dithiothreitol was a necessary component for the stability of partially purified activating enzyme. NaCl inhibited the coupled assay for activating enzyme. The pI of activating enzyme was determined to be 6.5. Activating enzyme is composed of a minimum of 336 amino acids and a minimum calculated Mr is 32,032. The Mr of activating enzyme was estimated to be 21,700 by analytical gel filtration and 32,800 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. An absorption maximum at 280 nm was observed for the activating enzyme.

Amino Acids↗
PubMed1983

[High potential iron-sulfur protein from Thiocapsa roseopersicina].

A high potential protein (HiPIP) containing a [4Fe-4S] cluster was obtained in a homogeneous state from the purple sulfur bacterium T. roseopersicina strain BBS. The EPR and absorption spectra are specific for this type of proteins. In the absorption spectrum the A283/A390 ratio equals to 2.25; Mr = 10 000, pI is 4.08, E0' = +328 mV. The reduced form of HiPIP was found to be more stable upon storage; T 1/2 is 40 min at 80 degrees C. HiPIP can be reduced by ascorbate, cysteine, 2-mercaptoethanol and sulfide as well as by formate, H2 and NADPH in the presence of corresponding enzymes. Chromatophores oxidize HiPIP in the light. This suggests that the latter takes part in the photosynthetic electron transfer chain of T. roseopersicina.

Chromatium↗
PubMed1983

Melanophore characteristics in a fresh-water teleost, Puntius conchonius (Ham.).

The present study is an attempt to determine the factors responsible for the melanophore pattern of the freshwater teleost, Puntius conchonius (Ham.) under normal background conditions (i.e., the existence of a large round black spot on the middle of the side above the posterior part of the anal fin and the dull shade of the rest of the body which is brownish on the dorsal part, referred here in the present study as the general body surface and silvery along the lateral and ventral part of the body). On the basis of nature of their branching pattern various morphological types of melanophores are classified in a scale from the dark spot area as well as the general body surface. There are as many as 7 types of melanophores termed as A, B, C, AB/AC (all system I deep melanophores) and a, b and c (all system I superficial melanophores). The integument of the fish, however, possesses 3 kinds of chromatophores namely--melanophores, xanthophores and iridophores. The identity of the dark spot as clearly maintained entity independant from the general body surface may be attributed to greater number of system I melanophores, greater melanin content in the system I and system II melanophores, smaller interspaces between system I and system II deep melanophores, greater anastomosing in the superficial melanophores, larger size of system I deep as well as superficial melanophores. The reverse order of the above mentioned factors is responsible for the dull-brownish shade of the general body surface of the fish. The dark spot toward the tail end in the fish, possibly may serve to intimidate or misdirect attack and thus facilitate escape.

Animals↗
PubMedDate not supplied

[Kinetic model of the operation of a 2-electron switch in the photosynthetic reaction center of bacteria].

A mathematical model, describing the binary oscillation of the concentration of semiquinone form of the secondary acceptor (ubiquinone) in photosynthetic reaction center of purple bacteria is proposed. This model takes into account both the changes of the ubiquinone state when the chromatophores are subjected to short flashes of light, and the successive dark relaxation of the semiquinone form. The model allows to calculate such characteristics as the dependence of the flash number, the stationary level of semiquinone form which is being established, when the flash number increases, the velocity which the concentration of semiquinone form is aspirating towards this stationary level and other characteristics. The model shows that the quantum yield of primary charge separation on the reaction center is higher after odd-number flashes then after even-number flashes.

Benzoquinones↗
PubMedDate not supplied

[Effect of pH on photoinduced electron transport in reaction center preparations from Rhodopseudomonas sphaeroides].

The effect of ph on kinetics of photo-induced electron transport process was studied on reaction centre preparations extracted by LDAO treatment of R. sphaeroides chromatophores (strain 1760-1). Reaction centre activity was found to be optimal at pH 7--9. Within this range of pH, the rate constant, KX1X2, for electron transfer from the primary FeQ acceptor complex (X1) to the secondary quinone acceptor X2 appeared to be invariant. On pH lowering from 7 to 5 the value of KX1X2 increases by several times. It abruptly drops, when pH is increased from 9 to 9.5. The nature of these phenomena including influence of pH on KX1X2 value is discussed.

Binding Sites↗
PubMed1981

[Structural-functional characteristics of photosynthetic reaction centers extracted by treatment with lauryldimethylamine oxide from Rhodopseudomonas sphaeroides (wild type)].

A method for isolation of photoactive reaction centers from Rps. sphaeroides (wild type) chromatophores, using lauryldimethylamine oxide (LDAO) as detergent, is described. The preparation obtained is free of a light-harvesting pigment-protein complex and cytochromes. A high degree of purity can be demonstrated from the adsorption indexes of the preparation equal to A280 : A800 = 1.2--1.3; A760 : A800 : A870 = 1 : 2 : 0.9. Data from polyacrylamide gel electrophoresis suggest that the integral protein component of the preparation is made up of three polypeptides with molecular weights of 30 000, 24 000 and 20 000. Under continuous illumination the preparation exhibits an effective electron transfer from the bacteriochlorophyll dimer (BChl)2 to a system of quinone acceptors (X1, X2). The ambient potential Em of (BChl)2 half-recovery was estimated as + 475 mV and pH 7.2. The rate constant for direct electron transfer from X1- to X2 is about 0.5 . 10(3) s-1 at 300 degrees K (0.01 M phosphate buffer; 0.05% LDAO, pH 7.2). The activity of this transfer is exponentially reduced with a decrease in temperature within the range of 300 to 230 degrees K, with an activation energy, Ea, of approximately equal to 8 kcal. The recombination rate constant of light-induced ion-radicals, (BChl)2+ and X1-, was found to be 5 . 10(-2) s-1 at 180 degrees K. The preparations thus obtained can be used for studying mechanisms of primary events in photosynthesis and electron-exchange conformations in the reaction center.

Bacterial Proteins↗
PubMedDate not supplied

[Debye-Waller factor of Rayleigh scattering of Mössbauer radiation at substances with strong conformation motions].

A model was developed to describe conformational motion of macromolecules. A new formula was derived for the Debye-Waller factor in accordance with this model. The model proposes the existence of fluidlike motions of fragments within the volume of some A3. The temperature dependence of Rayliegh scattering of Mossbauer radiation was studied and calculated for chromatophores.

Macromolecular Substances↗
PubMedDate not supplied

[Technique for the determination of the quantum yield of the primary process in the course of photosynthesis energy transformation. III. Experimental data obtained for different photosynthetic organisms].

A relative method in two modifications has been developed for determination of the quantum yield of primary photosynthesis energy conversion. The purple bacteria E. chaposhnikovii and Chr. minutissimum, R. rubrum chromatophores, cell extracts of E. shaposhnikovii, Rps. spheroides strains GA and R-26, pigment-protein complexes from green bacterium Chl. limicola and light subchloroplast particles, enriched in the photosystem I, were investigated. The quantum yields for all these objects were shown to be 90-98%. The accuracy of the relative method used is very high (within 2--4+). The photosynthetic units were proved to be of a multicentral type for all these systems. The quantum yield values permit estimation of the coefficient of efficiency of the primary conversion process as being approximately equal to 35-38% for bacteria and approximately equal to 50% plants.

Bacteria↗