Cyanide-linked dimer-monomer equilibrium of Chromatium vinosum ferric cytochrome c'

Cyanide binding to Chromatium vinosum ferricytochrome c' has been studied to further investigate possible allosteric interactions between the subunits of this dimeric protein. Cyanide binding to C. vinosum cytochrome c' appears to be cooperative. However, the cyanide binding reaction is unusual in that the overall affinity of cyanide increases as the concentration of cytochrome c' decreases and that cyanide binding causes the ligated dimer to dissociate to monomers as shown by gel-filtration chromatography. Therefore, the cyanide binding properties of C. vinosum ferricytochrome c' are complicated by a cyanide-linked dimer to monomer dissociation equilibrium of the complexed protein. The dimer to monomer dissociation constant is 20-fold smaller than that for CO linked dissociation constant of ferrocytochrome c'. Furthermore, the pH dependence of both the intrinsic equilibrium binding constant and the dimer to monomer equilibrium dissociation constant was investigated over the pH range of 7.0 to 9.2 to examine the effect of any ionizable groups. The equilibrium constants did not exhibit a significant pH dependence over this pH range.

Crystallization and characterization of Chromatium vinosum cytochrome c'

The dimeric high spin c-type cytochrome c' from Chromatium vinosum has been crystallized and the crystals characterized by x-ray diffraction. This cytochrome c' exhibits ligand-controlled dissociation from a dimer to a monomer upon binding carbon monoxide and represents an opportunity to obtain unique information concerning cooperativity in heme proteins. The C. vinosum cytochrome c' protein crystals are grown from polyethylene glycol 4000 and grow in both space group P2(1)2(1)2(1) (a = 49.2, b = 56.7, c = 98.8 A) and space group P2(1) (a = 55, b = 94, c = 50, beta = 106.1 A) depending upon the growth rate, with the P2(1)2(1)2(1) form favored at slower growth rates. The high resolution (2.0 A) atomic structure of the P2(1)2(1)2(1) form is being determined.

1H NMR characterization of Chromatium gracile high-potential iron protein and its ruthenium-modified derivatives. Modulation of the reduction potentials in low- and high-potential [Fe4S4] ferredoxins

The NMR spectra of the high-potential iron protein from the photosynthetic bacterium Chromatium gracile and its ruthenium-labeled (His-42 and His-20) derivatives are reported. The isotropically shifted resonances in both the oxidized and reduced forms show a complex pH dependence due to the presence of three ionizable residues (Glu-44, His-20, and His-42). Assignments have been made to specific residues and the spectral features compared to those of other bacterial HiPIP's. The decrease in the reduction potential with increasing pH for this class of proteins is attributed to stabilization of the oxidized state of the cluster by delocalization of electron density onto the neighboring Tyr-19 residue.

Lipopolysaccharides of Thiocystis violacea, Thiocapsa pfennigii, and Chromatium tepidum, species of the family Chromatiaceae

The lipopolysaccharides (LPS) of three species of purple sulfur bacteria (Chromatiaceae), Thiocystis violacea, Thiocapsa pfennigii, and the moderately thermophilic bacterium Chromatium tepidum, were isolated. The LPS of Thiocystis violacea and Chromatium tepidum contained typical O-specific sugars, indicating O-chains. Long O-chains were confirmed for these species by sodium deoxycholate gel electrophoresis of their LPS. Thiocapsa pfennigii, however, had short or no O-chains. The core region of the LPS of all three species comprised D-glycero-D-mannoheptose as the only heptose and 2-keto-3-deoxyoctonate. The lipid A, obtained from the LPS by mild acid hydrolysis, contained glucosamine as the main amino sugar. Amide-bound 3-hydroxymyristic acid was the only hydroxy fatty acid. The main ester-bound fatty acid in all lipid A fractions was 12:0. Mannose and small amounts of 2,3-diamino-2,3-dideoxy-D-glucose were common constituents of the lipid A of the three Chromatiaceae species investigated. All lipid A fractions were essentially free of phosphate.

Thioredoxin from Rhodospirillum rubrum: primary structure and relation to thioredoxins from other photosynthetic bacteria

Thioredoxin was isolated from a photosynthetic purple nonsulfur bacterium, Rhodospirillum rubrum, and its primary structure was determined by high-performance tandem mass spectrometry. The sequence identity of R. rubrum thioredoxin to Escherichia coli thioredoxin was intermediate to those of the Chlorobium thiosulfatophilum and Chromatium vinosum proteins. The results indicate that R. rubrum has an NADP-thioredoxin system similar to that of other photosynthetic purple bacteria.

Spectroscopic and ligand-binding properties of an oxygen-binding heme protein from Chromatium vinosum

Magnetic circular dichroism spectra were obtained for the oxidized and reduced forms of cyanide, azide and carbon monoxide complexes of an O2-binding hemeprotein isolated from the photosynthetic purple sulfur bacterium, Chronatium vinosum. Cyanide binding to the protein, which results in formation of a low-spin complex, was highly pH dependent with little complex formation observed at pH values near or below 7.

Properties of the reaction center of the thermophilic purple photosynthetic bacterium Chromatium tepidum

Reaction centers were purified from the thermophilic purple sulfur photosynthetic bacterium Chromatium tepidum. The reaction center consists of four polypeptides L, M, H and C, whose apparent molecular masses were determined to be 25, 30, 34 and 44 kDa, respectively, by polyacrylamide gel electrophoresis. The heaviest peptide corresponds to tightly bound cytochrome. The tightly bound cytochrome c contains two types of heme, high-potential c-556 and low-potential c-553. The low-potential heme is able to be photooxidized at 77 K. The reaction center exhibits laser-flash-induced absorption changes and circular dichroism spectra similar to those observed in other purple photosynthetic bacteria. Whole cells contain both ubiquinone and menaquinone. Reaction centers contain only a single active quinone; chemical analysis showed this to be menaquinone. Reaction center complexes without the tightly bound cytochrome were also prepared. The near-infrared pigment absorption bands are red-shifted in reaction centers with cytochrome compared to those without cytochrome.

The primary structure of thioredoxin from Chromatium vinosum determined by high-performance tandem mass spectrometry

The primary structure of thioredoxin, a redox protein isolated from Chromatium vinosum, was determined by high-performance tandem mass spectrometry, which permitted sequencing of the 14 peptides (ranging in length from 2 to 18 amino acids) generated by digestion with trypsin and of several peptides produced by Staphylococcus aureus protease. The mass spectrometrically determined molecular weights of the peptides from the latter digest were used to properly align the tryptic peptides, which could also be accomplished on the basis of the considerable homology with Escherichia coli thioredoxin. Finally, the molecular weight of the Chromatium thioredoxin was determined by mass spectrometry and found to be 11,748.0, in good agreement with 11,750.2 calculated for the proposed sequence. Although it was difficult to establish by mass spectrometry, five leucines and three isoleucines could be identified, leaving only eight undifferentiated.

Spectroscopic and kinetic properties of an oxygen-binding heme protein from Chromatium vinosum

Resonance Raman and electron paramagnetic resonance spectroscopy have been utilized to identify histidine as an axial heme ligand in a high spin, heme c-containing protein isolated from the photosynthetic purple sulfur bacterium Chromatium vinosum. Resonance Raman spectroscopy has also been used to characterize the CO adduct of the C. vinosum hemoprotein. Resonance Raman spectra of the heme site obtained within 10 ns of CO photolysis from the ferrous hemoprotein are virtually identical to those of the unligated protein, indicating that there is little or no rearrangement of the heme pocket in response to ligand photolysis. The equilibrium constant for CO binding to the ferrous hemeprotein was measured to be 1.7 X 10(-5) M-1 and the CO association rate constant determined to be 5.4 X 10(3) M-1 S-1. The quantum efficiency for photodissociation of the hemoprotein X CO complex was greater than or equal to 0.9.

Isolation, characterization, and comparison of a ubiquitous pigment-protein complex consisting of a reaction center and light-harvesting bacteriochlorophyll proteins present in purple photosynthetic bacteria

Protein complexes (photochemical reaction complex; PR complex) bound to both light-harvesting bacteriochlorophyll-1 (LH-Bchl-1) and reaction center Bchl (RC-Bchl) were purified from Rhodospirillum rubrum (wild and carotenoid-less), Rhodopseudomonas sphaeroides (wild), and Chromatium vinosum (wild). Another protein complex (LH-2 complex) bound to LH-Bchl-2 was also purified from Rps. sphaeroides. The bacteria were grown in the presence of a [14C]amino acid mixture. The purification procedure included molecular-sieve chromatography in the presence of cholate-deoxycholate, and non-equilibrated isoelectric electrophoresis with 3-[(3-cholamidopropyl)dimethylamino]-1-propanesulfonate. The purified complexes were separated into their constituent proteins by sodium dodecylsulfate-polyacrylamide gel electrophoresis. The molar ratios of the proteins were determined by comparing their radioactivities divided by their molecular weights after consideration of the molecular masses of the complexes. The PR complexes all contained per mol: 1 mol each of RC H-, M-, and L-subunits, 10-13 (probably 12) mol each of two other proteins with molecular weights of 11-12K and 8-11K, 28-32 mol Bchl, 13-15 mol carotenoids (except in the carotenoid-less mutant), 2.6-3.9 mol ubiquinone (or menaquinone in Chr. vinosum), and 53-79 mol phosphate without phospholipid. The LH-2 complex contained per mol: 1 mol 52K protein, about 13 (probably 12) mol each of 9K and 8K proteins, 30 mol Bchl, 10 mol carotenoids, and 38 mol phosphate without phospholipid. The PR complexes and LH-2 complex showed similar X-ray diffraction patterns, implying that they had similar, highly organized molecular structures.

Resonance Raman characterization of a novel, oxygen-binding heme protein from Chromatium vinosum

Resonance Raman spectroscopy was employed to characterize the local heme environment of a high-spin, ligand-binding heme protein from Chromatium vinosum (Chromatium high-spin hemoprotein). High-frequency spectra obtained with both B- and Q-band excitation were found to resemble qualitatively those of deoxyhemoglobin (HbA). Differences between HbA and Chromatium high-spin hemoprotein spectra can be assigned to either the effects of a covalent linkage of the heme vinyls to the protein matrix or alterations in the heme-proximal ligand bonding interaction. Both kinematic and electronic effects were evident. The behavior of heme core-size sensitive modes and low-frequency modes in Chromatium high-spin hemoprotein may be an indication of distortions in the heme geometry of Chromatium high-spin hemoprotein relative to HbA. The effects of covalent bonding of the heme peripheral vinyls upon the vibrational, electronic, and geometric characteristics of the heme active site in Chromatium high-spin hemoprotein are discussed.

Terminal steps of bacteriochlorophyll a phytol formation in purple photosynthetic bacteria

Four chemically different bacteriochlorophylls (Bchls) a esterified with geranylgeraniol, dihydrogeranylgeraniol, tetrahydrogeranylgeraniol, and phytol have been detected by high-pressure liquid chromatography in cell extracts from Rhodopseudomonas sphaeroides and Chromatium vinosum. Bchl a containing phytol is the principal component, and the other three Bchls a comprise about 4% of the total Bchls a in stationary-phase cells of R. sphaeroides and C. vinosum. The high levels of the minor pigments occur in the beginning of Bchl a phytol formation, indicating that they are not degradation products, but intermediates of Bchl a phytol formation.

Cytochromes and anaerobic sulfide oxidation in the purple sulfur bacterium Chromatium warmingii

Two soluble acidic c-type cytochromes--c' and c-552--were isolated by ion exchange chromatography, gel filtration and ammonium sulfate fractionation. Cytochrome c' is a high-spin cytochrome with maxima at 399 nm, 490 nm, and 634 nm in the oxidized form and at 550 nm, 425 nm and a characteristic shoulder at 434 nm in the reduced state. The best purity index obtained (A280/A399) was 0.35. Cytochrome c' is autoxidizable, has a molecular weight of 12000 (estimated by sodium dodecylsulfate electrophoresis), a midpoint redoxpotential of +10 mV and an isoelectric point at pH 4.0. The reduced cytochrome c' reacts with carbon monoxide. The reaction is reversible. Cytochrome c-552 shows maxima at 552 nm, 523 nm and 417 nm in the reduced form and at 408 nm in the oxidized state. The best purity index obtained (A280/A408) was 0.94. Cytochrome c-552 has a molecular weight of 30000 and an isoelectric point between pH 4.3 and 5.0. Chromatium warmingii also contains a membrane-bound cytochrome c-552. During anaerobic sulfide oxidation, elemental sulfur and sulfate were formed at the same time. When all sulfide was consumed by the cells, the remaining intracellular elemental sulfur was further oxidized to sulfate.

Molecular properties of high potential iron sulfur protein of Chromatium warmingii

High potential iron sulfur protein (HIPIP) of the purple sulfur bacterium Chromatium warmingii was purified to homogeneity by ion exchange chromatography, gel filtration and ammonium sulfate fractionation. The acidic protein was isolated in the reduced form. The best purity index (A280/A388) obtained was 2.52, and 3.8 mumol of the protein was isolated out of 100 g wet cell material. The molecular weights estimated by sodium dodecylsulfate polyacrylamide gel electrophoresis and gel filtration through Sephacryl S-200 were 8900 and 10 500, respectively. The protein has an isoelectric point at pH 3.6 for the reduced form and at pH 3.8 for the oxidized form, and a midpoint redox potential of +355 mV. One mol of HIPIP contains 4 mol nonheme iron and 4 mol acid-labile sulfur.

Partial purification and characterization of two soluble c-type cytochromes from Chromatium vinosum

Two c-type cytochromes from Chromatium vinosum have been partially purified and characterized. Cytochrome c550, which appears to function as an electron carrier in the cyclic electron transport chain of this photosynthetic purple sulfur bacterium, has a molecular weight of approximately 15,000 and an oxidation-reduction midpoint potential (Em) of +240 mV at pH 7.4. It has (in the reduced form) an alpha band at 550 nm and a beta band at 520 nm. Cytochrome c551 is characterized by absorbance maxima at 354 and 409 nm in the oxidized form and 418, 523, and 551 nm in the reduced form. The reduced cytochrome reacts with CO. Cytochrome c551 is a monomeric protein with a molecular weight of 18,800 +/- 700 and Em = -299 +/- 5 mV (pH independent between pH 6.3 and 8.0). It appears to lack a methionine axial ligand as indicated by the absence of an absorbance band at 695 nm in the oxidized form.

Polar lipids in phototrophic bacteria of the Rhodospirillaceae and Chromatiaceae families

The polar lipids of photosynthetic purple bacteria of the genera Chromatium, Thiocapsa, Thiocystis, Ectothiorhodospira, Rhodopseudomonas, Rhodospirillum, and Rhodomicrobium were analyzed. Characteristic compositions of the polar lipids were found for most of the Rhodospirillaceae and Chromatiaceae species. Phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin were the major phospholipids in most species. Phosphatidylcholine was present as a major component in all species of the genus Ectothiorhodospira, but was not detected in the remaining Chromatiaceae. It was also present in most of the Rhodospirillaceae species. No glycolipids were found in any of the Ectothiorhodospira species. In the Rhodospirillaceae, the glycolipids mono- and digalactosyl diglycerides were generally absent. Sulfoquinovosyl diglyceride was present in significant amounts in at least three species of the Rhodospirillaceae and may have been present in most of them, but only in traces. All of the Chromatiaceae species contained several glycolipids, one of which was similar to monogalactosyl diglyceride. Ornithine lipids were found in large amounts in most Rhodospirillaceae, but were absent in Ectothiorhodospira and in the other Chromatiaceae. The species examined could be divided into three groups on the basis of their lipid composition: (i) the genus Ectothiorhodospira; (ii) the remaining Chromatiaceae; and (iii) the Rhodospirillaceae. The data presented are compared with those available in the literature, and differences from other phototrophic organisms are discussed.

Near-infrared absorption spectra of light harvesting bacteriochlorophyll protein complexes from Chromatium vinosum

Light harvesting (LH) bacteriochlorophyll (Bchl) protein complexes were isolated from chromatophores of Chromatium vinosum, by the combination of detergent solubilization, sodium dodecylsulfate (SDS) polyacrylamide gel electrophoresis (PAGE) and hydroxyapatite chromatography. Addition of the absorption spectra of these complexes reproduced the absorption spectrum of chromatophores from which these complexes were derived. This result led to the conclusion that these isolated complexes retained the near-infrared absorption spectra which these complexes showed as they existed in chromatophores. Two kinds of spectrally different chromatophores were obtained under different culture conditions. One of them contained two kinds of LH Bchl protein complexes; B890 containing and B850-B800 containing complexes, and the other contained, in addition, B820-B800 containing complex. B890 containing complexes from the two types of chromatophores were spectrally similar, whereas B850-B800 containing complexes were not the same with respect to the location of absorption maxima and the content of B850. It was shown that the variation of the near-infrared absorption spectra of the chromatophores is due to not only the variation of the ratio of complexes but also the variation of the absorption spectrum of a particular complex.

Formation of super-reduced Chromatium high-potential iron--sulphur protein in aqueous solution by pulse radiolysis

Both the oxidized and reduced forms of Hipip (high-potential iron--sulphur protein) are reduced (approx. 30% yields) by eaq.- in a single-stage process, rate constants 1.7 x 10(10) and 1.8 x 10(10) M-1 . s-1 respectively, at 25 degrees C, pH 7.0 (5 mM-phosphate). Super-reduced Hipip, which is formed in the latter case, has a spectrum which closely resembles that of reduced ferredoxin, i.e. Fe4S4 (SR)4(3-) clusters. The spectrum is stable over 2 s periods investigated. Super-reduced Hipip is reoxidized with O2, rate constant 4.8 x 10(6) M-1 . s-1 at 25 degrees C.

Isolation and partial characterization of the major outer membrane protein of Chromatium vinosum

The 42,000 major outer membrane protein of Chromatium vinosum was purified by a combination on ion-exchange chromatography, gel filtration, and isoelectric focusing. Upon isoelectric focusing, the final material produced four major hands. Three of the four bands were isolated and analyzed for similarity or differences. Protease peptide maps and cyanogen bromide maps of the three isoelectric species were identical. When the isolated isoelectric species were refocused, each produced multiple isoelectric species, suggesting that the procedure used was generating the multiple charged species. Protease treatment of the isolated outer membrane produced a 31,000 fragment from the 42,000 protein. This fragment was isolated by preparative sodium sulfate-polyacrylamide gel electrophoresis. Although the amino acid compositions of the 42,000 protein and its 31,000 trypsin fragment were different, their polarity index was the same (45%). The amino-terminal sequences of the 42,000 protein and 31,000 trypsin fragment were identical, and it concluded that the amino-terminal was buried in the membrane.

[Linear dichroism of pigments associated with spherical chromatophores. Models of orientation in polyacrylamide gels]

Linear dichroism and orientation of pigments in chromatophores of photosynthetic bacteria Chromatium minutissimum and Rhodospirillum rubrum using a novel method of orientation in polyacrylamide gel was studied. A model is proposed for orientation of spherical membranes of chromatophores or other similar vesicules. The value of linear dichroism is derived for known deformation of the gel and a certain angle between the transition dipole and a unit vector perpendicular to the membrane plane. The analysis of linear dichroism spectra permits calculation of angles between the normal to the membrane and the transition dipoles in Chr. minutissimum 65 degrees +/- 1.5 degrees (890 nm absorption band), 63 degrees +/- 1 degree (860 nm), 63 degrees +/- 1 degree (800 nm), 45.5 degrees +/- 1 degree (590 nm), 50.5 degrees +/- 0.5 degree (450--550 nm) and in Rsp. rubrum: 71 degrees +/- 1.5 degree (890 nm), 66.5 degrees +/- 1 degree (870 nm), 69 degrees +/- 1.5 degree (800 nm), 37 degrees +/- 0.5 degree (590 nm), 49.5 degrees +/- 0.5 degree (450--550 nm). The 860 nm band shift to shorter wave-lengths observed in Chr. minutissimum chromatophores treated with 0.01 M potassium ferricyanide is not related to reorientation of transition dipoles, but rather to certain changes of lipid-protein environment.

Chromophore interactions in flavocytochrome c552: a resonance Raman investigation

Resonance Raman spectra with both Soret and visible excitation have been obtained for Chromatium flavocytochrome c552 and its isolated diheme subunit under varying conditions of pH and inhibitor binding. The spectra are generally consistent with previously established classification schemes for porphyrin ring vibrations. The presence of covalently bound flavin in the protein was apparent in the fluorescent background it produced and in flavin-mediated photoeffects observed in heme Raman spectra obtained at high laser power. No flavin modes were present in the Raman spectra, nor was any evidence of direct heme-flavin interaction found by using this technique; however, a systematic perturbation of heme B1g vibrational frequencies was found in the oxidized holoprotein. The heme vibrational frequencies of c552 are compared to those of the diheme peptide and of other c-type cytochromes. They are consistent with an interpretation that involves pH-dependent changes in axial ligation and treats the hemes and flavin as isolated chromphores communicating via protein-mediated interactions.

[Effect of light intensity on the content of bacteriochlorophyll and on the growth of phototrophic marine sulfur bacteria]

Eight strains of Chromatiaceae isolated from marine sediments are cultivated under light intensities of 50-5000 lx. A decreased in the light intensity brings about an increase in the specific bacteriochlorophyll content and also in the length of development. In certain strains, the increase in pigment contents partly compensates for the loss in light intensity, up to the maximum concentration of bacteriochlorophyll. This mechanism is only a physiological compatibility which ensures the survival of these organisms under feeble light intensities.

Characterization of the cell wall and cell wall proteins of Chromatium vinosum

Highly purified cell walls of Chromatium vinosum were isolated by differential centrifugation, with or without Triton X-100 extraction. The isolated material had a protein composition similar to that of cell walls obtained by sucrose density gradient centrifugation. Twenty-two proteins were reproducibly detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A 42-kilodalton protein was shown to account for 65% of the total cell wall protein. The majority of cell wall proteins were solubilized in sodium dodecyl sulfate at room temperature; however, they existed as high-molecular-weight complexes unless heated to 45 degrees C or above. The cell wall contained one heat-modifiable protein which migrated with an apparent molecular weight of 37,400 when solubilized at 70 degrees C or below, but which migrated with an apparent molecular weight of 52,500 if solubilized at 100 degrees C. The electrophoretic mobility of three proteins was modified by 2-mercaptoethanol. The majority of C. vinosum cell wall proteins had isoelectric points between pH 4.5 and 5.5, and the 42-kilodalton protein focused at pH 4.9. No proteins were detected which were analogous to the lipoprotein or peptidoglycan-associated proteins of the Enterobacteriaceae. Nearest-neighbor analysis with a reducible, cross-linking reagent indicated that three proteins, including the 42-kilodalton protein, associated with themselves. Most of the cell wall proteins were partially accessible to proteases in both intact cells and isolated cell walls. Protease treatment of the whole cell or isolated cell wall digested approximately an 11,000-molecular-weight portion of the 42-kilodalton protein.

[Ratio of metals during changes in the metabolism of photosynthetic bacteria]

The content of polyvalent metals was determined in the photosynthetic bacteria Rhodopseudomonas capsulata (Athiorhodaceae) and Chromatium vanda (Thiorhodaceae) isolated from the sediments of Lake Vanda in the Antarctic when the conditions of growth, photoheterophic and photoautotrophic, were changed. The ratio between Fe and Mn, Cu, V, Ni, Co, Cr was studied. The utilization of all polyvalent metals, Mn and Cr in particular, relatively increased in the conditions of autotrophic growth. Changes in the composition of bacterial cells (the content of protein, lipophilic substances, flavin) and their enzymatic activity (hydrogenases) were also assayed. Apparently, chemical composition may be used as a criterion for determining the taxonomy of organisms and the ecological conditions of their habitat.

Modifiable chromatophore proteins in photosynthetic bacteria

The chromatophores of Chromatium vinosum, as well as six other photosynthetic bacteria, contained two or more proteins which were insoluble when heated in the presence of sodium dodecyl sulfate (SDS) and 2-mercaptoethanol (beta-ME). When the chromatophores were dissolved at room temperature in SDS-beta-ME, these proteins were present in the SDS-polyacrylamide gel electrophoresis profiles, but when the samples were dissolved at 100 degrees C, they were absent or considerably diminished. When one-dimensional gels of chromatophores solubilized at room temperature were soaked in the SDS-beta-ME solution and heated to 100 degrees C and the gels were run in a second dimension, the proteins became immobilized in the original first-dimension gel, where they could be detected by staining. The two major proteins so affected in C. vinosum had apparent molecular weights of 28,000 and 21,000. The chromatophores of several other photosynthetic bacteria also contained predominant proteins between 30,000 and 19,000 molecular weight, which became insoluble when heated in the presence of SDS and beta-ME. In at least two of the species examined, these appeared to be reaction center proteins. The conditions causing the proteins to become insoluble were complex and involved temperature, SDS concentration, and the presence of sulfhydryl reagents. The chromatophores of four of the Chromatiaceae species and two strains of one of the Rhodospirillaceae species examined had a protein-pigment complex that was visible in SDS-polyacrylamide gel profiles of samples dissolved at room temperature but was absent in samples dissolved at 100 degrees C.

Isolation and characterization of a membrane-bound, low-potential c-type cytochrome from purple photosynthetic bacteria, with special reference to Rhodospirillum rubrum

Other investigators have isolated soluble, low-potential, c-type cytochromes (cytochrome c3) from a few photosynthetic procaryotes, i.e., a cyanobacterium and two species of purple nonsulfur bacteria. However, such cytochromes appeared to be absent from other purple bacteria, including Rhodospirillum rubrum and Chromatium vinosum. We now report evidence for the presence of low-potential c-type cytochromes in these two species, in which they were found to be bound to the photosynthetic membranes. Evidence for a membrane-bound, low-potential c-type cytochrome was also found in Rhodopseudomonas sphaeoides. The low-potential c-type cytochrome of R. rubrum was solubilized by a Triton X-100 treatment of chromatophores and was partly purified. It was found to have a molecular weight of about 17,000, a midpoint oxidation-reduction potential of -192 mV, and an alpha-absorption peak at 552 nm. It appears that low-potential c-type cytochromes may be present in all purple photosynthetic bacteria, of both the sulfur and the nonsulfur types.

Cluster characterization in iron-sulfur proteins by magnetic circular dichroism

We report magnetic circular dichroism (MCD) spectra of 4-Fe iron-sulfur clusters in the iron-sulfur proteins Chromatium high-potential iron protein (HIPIP), Bacillus stearothermophilus ferredoxin and Clostridium pasteurianum ferredoxin. The MCD is found to vary significantly with cluster oxidation state but is relatively insensitive to the nature of the protein. The spectra obtained are compared with the corresponding spectra of iron-sulfur proteins containing 2-Fe clusters. It is concluded that MCD is useful for the characterization of iron-sulfur cluster type and oxidation state in iron-sulfur proteins and is superior for this purpose to absorption and natural circular dichroism spectroscopy.

[Molecular organization of the long-wave complexes of purple photosynthesizing bacteria. Effect of pronase on the B890 complex of Chromatium minutissium and Rhodopseudomonas palustris]

The pronase action on the long-wave complexes B890 from two different purple bacteria has been investigated. Differences in the kinetics of decrease of the reaction center photochemical activity of electron-donor activity of cytochromes and of destruction of Bx890 (875) forms have been discovered. Different rates of the proteolysis of RC proteins were revealed by SDS-gel-electrophoresis. The heavy protein of RC was the first to degrade. The photochemical transformations deltaA890(875) in B890 complexes was observed during formation of peptides with molecular weight about 17 000 from two other RC proteins. On the basis of obtained data the model of molecular organization of B890 complexes from purple bacteria is discussed.

Location of O-methyl sugars in antigenic (lipo-)polysaccharides of photosynthetic bacteria and cyanobacteria

An attempt was made to localize a number of O-methyl sugars in lipopolysaccharides and antigenic polysaccharides isolated from photosynthetic bacteria and from cyano-bacteria. Methylation analysis with [2H3]methyl iodide as methylating agent was the method of choice. One has to differentiate between (lipo-)polysaccharides having only trace amounts (less than 1% of polymer dry weight) of O-methyl sugars and those having them in larger amounts (more than 4% of polymer dry weight). In the former case O-methyl sugars occupy either non-reducing or reducing terminals. When present in larger quantities they may be present as part of each repeating unit either in chain-linked or in terminal positions or in both. A possible role of O-methyl sugars in biosynthesis of O-chains, and their contribution to the lipophilic character of the cell surface are discussed.

The preparation and characterization of different types of light-harvesting pigment-protein complexes from some purple bacteria

A general strategy, with some specific examples, is given for the isolation and purification of detergent-soluble, antenna pigment-protein complexes from the photosynthetic membranes. Absorption, fluorescence and circular dichroism spectra, and the pigment and protein composition of B800-B850-protein and B890-protein complexes of some purple bacteria (Rhodospirillum rubrum, Rhodopseudomonas sphaeroides and Rps. capsulata and Chromatium vinosum) are discussed. We conclude that there are probably two major classes of antenna carotenochlorophyll-proteins in purple bacteria containing bacteriochlorophyll a: a B890 complex which has one carotenoid and two bacteriochlorophyll molecules in the minimal unit (probable molecular weight around 20,000), and a B800 + B850 complex which has one carotenoid and three bacteriochlorophyll molecules in a similar-sized minimal unit. The whole cell spectrum of any purple bacterium can be reconstituted by combining different proportions of the spectra of these two complexes with that of the photochemical reaction centre.

[Study of the state of intracellular iron in photosynthesizing purple sulfur bacteria using the Mossbauer effect]

The work presents the results of the first stage of the study on the valent and structural state and function of the iron atoms in the donor-acceptor environment of the photosynthetic reaction centres of purple bacteria. 57Fe was introduced by cultivating the microorganisms in a medium enriched in this isotope. At 77 K the maxima observed in the Mössbauer spectra in intact freeze-dried cells at a speed of +2 mm/s and --1 mm/s are attributed to doublets 1.11 with the isomer ahifts of 1.3 and 0.5 mm/s respectively and the constants of the quadrupole splitting (Q.S.) of 2 mm/s and 2.2 mm/s. These are presumed to arise from cytochromes type c. The Mössbauer parameters of the intense assymetric quadrupole-split doublet of a more complex nature in the mid of the spectrum with line widths of 0.5 to 7.0 mm/s and 0.5 to 1.5 mm/s fit to these of bacterial ferredoxin. From the analysis of the control and dithionite-treated samples of the temperature dependency of the observable parameters over a temperature range of 77 to 300 K it can be concluded that in cells the iron atoms are present in various valency and spin states and the relation between the redox states of the iron atoms is dependent, in particular, on the age of the culture. The Mössbauer spectra of the cell fragments indicate that most of the intracellular iron, first of all the heme iron, is bound to the fraction of photosynthetic membranes.

New stereochemical analogies between iron-sulfur electron transport proteins

Active sites of Chromatium high potential iron protein (HiPIP) and Pseudomonas Aerogenes ferredoxin can be brought into equivalent orientations by assuming that their Fe4S4Sgamma4 clusters have the effective symmetry of the non-axial molecular point group Cs. Previously undetected analogies between the two proteins emerge as a result of selecting a common orientation in this mammer. Polypeptide segments connecting Cys 46 to Cys 63 in HiPIP and Cys 18 to Cys 35 in ferredoxin are analogous in the sense that they are the same length, they connect equivalent cysteinyl sulfur atoms, and they have similar, twisted antiparalled beta conformations. Tyrosine residues 19 (HiPIP) and 2 (ferredoxin) are analogous in the sense that they interact closely with equivalent inorganic sulfur atoms. To a good approximation, interactions with the polypeptide backbone and with tyrosine side chains in the two proteins place their Fe4S4Sgamma4 moieties into diastereomeric environments, which would be expected to induce different physical and chemical behavior. Circular dichroism spectra of native and super reducible HiPIP (Cammack, R. (1973) Biochem. Biophys. Res. Commun. 54, 548-554) suggest that this relationship can help to explain the contrasting oxidoreduction properties of the two proteins.

Biological and physicochemical properties of the lipopolysaccharide of Chromatium vinosum

The lipopolysaccharide (LPS) of Chromatium vinosum has anticomplementary activity. This anticomplementary activity is destroyed by alkaline digestion of the LPS and is suppressed by both Mg2+ and Ca2+ ions. Treatment of the LPS with ethylenediaminetetraacetic acid, sodium deoxycholate, or dimethyl sulfoxide did not affect its toxicity toward mice; however, alkaline-treated LPS was not toxic. Treatment of the LPS with sodium deoxycholate, dimethyl sulfoxide, or sodium dodecyl sulfate resulted in reversible dissociation into subunits. Aggregation of the subunits into the original form was achieved by removing the dispersing agent by dialysis against distilled water followed by freezing and thawing. Electron micrographs of phenol-extracted LPS showed long filaments. Electron micrographs of sodium deoxycholate- and sodium dodecyl sulfate-treated and dialyzed LPS showed a mixture of small subunits and short filaments, whereas dimethyl sulfoxide-treated and dialyzed LPS contained only small ovoid spheres. The LPS produced an ordered series of multiple bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A similar banding pattern was observed for Salmonella abortus-equi and Proteus mirabilis LPS. The C. vinosum LPS appears to be mitogenic for mouse spleen cells.

[Concentration of polyvalent metals following a change in the metabolism of Chromatium vinosum]

The composition of polyvalent metals (Fe, Mn, Cu, Ti, Ni, Co, V, Cr) was compared during photoheterotrophous and autotrophous growth of Chromatium vinosum. A comparatively high content of Mn and Cr, i. e. metals whose amount increases in the course of evolution of photoautotrophous organisms, is typical of the bacterium after autotrophous growth. An increase in the concentration of Ti, i. e. a metal involved in the reduction reactions of the cells, is characteristic of photoheterotrophous growth. As metabolism changes, differences are found in the content of protein, lipophilic substances, thioesters, flavin, and in the hydrogenase activity. These differences are discussed with respect to the role of polyvalent metals in metabolism of Chromatium vinosum.

Isolation and characterization of the lipopolysaccharide of Chromatium vinosum

Lipolysaccharide was isolated from Chromatium vinosum by phenol/water extraction. The lipopolysaccharide is found exclusively in the phenol phase and can be cleaved into a sugar moiety and a lipid A fraction by hydrolysis in 10% acetic acid at 100 degrees C for 3-4 h. The sugar moiety contains the neutral sugars 3-O-methyl-D-ribose, D-ribose, L-arabinose, mannosamine and glucose, and smaller quantities of D-rhamnose, D-glycero-D-manno-heptose (tentatively identified), quinovosamine and 2-keto-3-deoxyoctonate. L-glycero-D-manno-heptose was not detected. The 2-keto-3-deoxyoctonate linkage in C. vinosum lipopolysaccharide is more resistant to acid hydrolysis than that of Escherichia coli. The lipid A fraction contains glucosamine, mannose and the fatty acids of the lipopolysaccharide. The major fatty acid is beta-hydroxymyristic acid, with smaller amounts of lauric and palmitic acids as well as 14-carbon mono-unsaturated fatty acid, also being present. The phosphorus content of the C. vinosum lipopolysaccharide was found to be approximately 0.1%. Erythrocytes sensitized with alkali-treated C. vinosum lipopolysaccharide were agglutinated by antisera prepared against heat-killed cells. Untreated or heat-treated lipopolysaccharide did not sensitize erythrocytes. The lethal toxicity to mice of the C. vinosum lipopolysaccharide is about one-tenth as that from Salmonella abortus equi.

NH---S hydrogen bonds in Peptococcus aerogenes ferredoxin, Clostridium pasteurianum rubredoxin, and Chromatium high potential iron protein

Results from refinement of the crystal structures of P. aerogenes ferredoxin and C. pasteurianum rubredoxin determined by x-ray diffraction show that there are 15-18 NH---S bonds in the former and six in the latter with lengths in the range 3.1-3.9 A. Earlier tritium exchange experiments are consistent with the presence of these hydrogen bonds in the ferredoxin structure and show that more peptide hydrogen atoms are available for exchange in apoferredoxin than in intact ferredoxin. Four types of NH---S bonds are observed and two of these are geometrically similar to the two types of 3(10) NH---O bonds. The existence of more NH---S bonds in ferredoxin than in high potential iron protein suggests why the -2 form of the Fe4S4 cluster is preferred in ferredoxin over the -1 form found in high potential iron protein. From comparison of Cys-X-Y-Cys sequences in rubredoxin, ferredoxin, and high potential iron protein we suggest that two Cys-X-Y-Cys-Z sequences, where Z may have conformation angles similar to glycine, are required to make a one-iron cluster, no more than one Cys-X-Y-Cys-Z-Gly sequence is required to form a Fe2S2 ferredoxin, and a Cys-X-Y-Cys-Gly sequence where Y has a conformation such that the cysteines bond to different iron atoms is necessary to form the tetrameric cluster.