Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Halobacterium”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 541 records · Page 30Linked to original sources
PubMed1986

tRNA binding capacities of ribosomal subunits from the archaebacterium Halobacterium halobium.

tRNA saturation experiments were performed with ribosomal subunits from the extreme halophilic archaebacterium Halobacterium halobium. In the presence of poly(U) the 30S subunit could bind equally well one AcPhe-tRNAPhe, Phe-tRNAPhe, or deacylated tRNAPhe molecule, respectively. Binding experiments with a mixture of two differently labeled tRNA species revealed that all three kinds of tRNA bound to one and the same binding site on the 30S subunit. Poly(U) dependent binding to the 50S subunit was insignificant for AcPhe-tRNA and Phe-tRNA. In the absence of poly(U) both AcPhe-tRNAPhe and Phe-tRNAPhe showed no significant binding to either subunit, whereas the binding of deacylated tRNAPhe could not be clearly determined. These results are in good agreement with those obtained from ribosomal subunits of the eubacterium Escherichia coli.

Acylation↗
PubMed1985

Transcription and excision of a large intron in the tRNATrp gene of an archaebacterium, Halobacterium volcanii.

The archaebacterium Halobacterium volcanii contains a single expressed gene for tRNATrp. This gene is interrupted, at a position corresponding to two nucleotides 3' to the anticodon, by an 105-base pair intervening sequence. Northern hybridization experiments show that the gene is transcribed in its entirety in vivo into a precursor of at least 180 nucleotides, and that one of the products of post-transcriptional processing is a 105-nucleotide species containing intron-specific sequences.

Base Sequence↗
PubMed1973

Structure determination of the glycolipid sulfate from the extreme halophile Halobacterium cutirubrum.

A sulfur-containing glycolipid, accounting for ca. 25% of the total polar lipids, has been isolated from the extreme halophile Halobacterium cutirubrum. The ammonium salt of the lipid was found to have the molecular formula C(61)H(117)O(21)S.NH(4), and on strong acid hydrolysis it yielded 2,3-di-O-phytanyl-sn-glycerol, glucose, mannose, galactose, and sulfate in equimolar proportions. Infrared and NMR spectra indicated the presence of a secondary sulfate group. Solvolysis of the lipid in 0.004 m HCl in tetrahydrofuran resulted in rapid release of inorganic sulfate and formation of galactosyl-mannosyl-glucosyl diphytanyl glycerol ether. With higher acid concentration (0.25 m methanolic HCl), stepwise hydrolysis of monosaccharide units occurred, giving mannosyl-glucosyl glycerol diphytanyl ether and monoglucosyl glycerol diphytanyl ether. The position of attachment of the sugars and of the sulfate group was determined by methylation of the free acid form of the glycolipid sulfate, followed by acid hydrolysis and gas-liquid chromatographic analysis of the partially methylated sugars as the alditol acetates. The configuration of the glycosidic linkages was established both by optical rotation measurements and by specific enzymatic hydrolysis. The results obtained established the structure as 2,3-di-O-phytanyl-1-O-[beta-d-galactopyranosyl-3'-sulfate-(1' -->6')-O-alpha-d-mannopyranosyl-(1' --> 2')-O-alpha-d-glucopyranosyl]-sn-glycerol.

Chromatography↗
PubMed1969

Occurrence of squalene, di- and tetrahydrosqualenes, and vitamin MK8 in an extremely halophilic bacterium, Halobacterium cutirubrun.

The nonpolar (acetone-soluble) lipids of the extremely halophilic bacterium, Halobacterium cutirubrum, were found to consist of red carotenoid pigments (43%) and squalenes (48%) with a small amount of a vitamin K-type quinone. The squalenes were shown by n.m.r. and mass spectra to consist of the fully isoprenoid squalene (S; C(30)H(50)), dihydrosqualene (S(2); C(30)H(52)), and tetrahydrosqualene (S(4); C(30)H(54)) in the ratio of 1.0:0.4:0.1. S(2) probably has one reduced internal isoprenoid group, and S(4) has one internal and one terminal reduced isoprenyl group. The vitamin K-type quinone was shown by n.m.r. and mass spectra to have a C(40) isoprenoid side chain, and is thus identified as menaquinone-8 (MK-8).

Alkenes↗
PubMedDate not supplied

[Picosecond flash photolysis of Halobacterium halobium bacteriorhodopsin at room and low temperatures].

The primary stage of photoexcitation of bacteriorhodopsin from Halobacterium halobium upon the action of ultrashort (tau equal to 25 ps) laser impulse of 530 nm wavelength and of energy 2.5.10(-3) J has been studied. The primary photoproduct with a maximum of 630 nm is shown to occur in the differential spectrum in a time less than 25 ps both at room temperature (+20 degrees C) and at a low temperature (-150 degrees C).

Bacteriorhodopsins↗
PubMedDate not supplied

[Spectral transformations of photoproducts in Halobacterium halobium cells].

Long-living spectral products observed earlier in purple membranes (PM) are discovered in the cells of Halobacterium halobium (Hh) under the action of yellow light. Blue spectral region of the light has been found to be optimal for PM arising in the cells cultivated under light. On the basis of the changes discovered in the optical spectra of Hh we may suppose that PM arising in the cells, is the dark processes, occur due to a hypothetic enzyme, which appears under light. The rate of PM arising is maximal during the periods of thermogenesis maximum.

Bacteriorhodopsins↗
PubMed1978

Nucleotide sequence of Halobacterium cutirubrum ribosomal 5 S ribonucleic acid. An altered secondary structure in halophilic organisms.

The nucleotide sequence of ribosomal 5 S RNA from a halophilic bacterium, Halobacterium cutirubrum, grown in 4 M sodium chloride is U-U-A-A-G-G-C-G-G-C-C-A-U-A-G-C-G-G-U-G-G-G-G-U-U-A-C-U-C-C-C-G-U-A-C-C-C-A-U-C-C-C-G-A-A-C-A-C-G-G-A-A-G-A-U-A-A-G-C-C-C-G-C-C-U-G-C-G-U-U-C-C-G-G-U-C-A-G-U-A-C-U-G-G-A-G-U-G-C-G-A-G-C-C-U-C-U-G-G-G-A-A-A-U-C-C-G-G-U-U-C-G-C-C-G-C-C-U-A-C-U. This nucleotide sequence is the longest prokaryotic 5 S rRNA to be reported and unlike other 5 S species does not contain a terminal mononucleoside diphosphate residue at its 5'-end. When compared to other 5 S rRNA's, the sequence homology is greatest (about 68%) with Bacillus subtilis; there is a lower but similar degree of homology (about 58%) with either Escherichia coli or human 5 S RNA. The comparisons further indicate that among 5 S RNA's, eleven of the nucleotide residues are unique to H. cutirubrum. Estimates of the secondary structure of the H. cutirubrum 5 S RNA molecule contain one additional stable hairpin loop which is not found in other 5 S rRNA species; this unusual structure is probably an adaptation to the high salt environment within H. cutirubrum cells.

Base Sequence↗
PubMed1984

Halobacterium volcanii tRNAs. Identification of 41 tRNAs covering all amino acids, and the sequences of 33 class I tRNAs.

Transfer RNAs of Halobacterium volcanii, an archaebacterium, were separated by two-dimensional gel electrophoresis and sequenced by a combination of methods. A total of 41 tRNAs, at least one for each amino acid, were identified. These are five tRNAs for Leu, four for Gly, three each for Ala, Arg, Pro, and Ser, two each for Glu, Ile, Lys, Met (initiator and noninitiator), Thr, and Val, and one each for the remaining eight amino acids. As in eucaryotes, only Leu and Ser tRNAs are class II (large extra arm). The sequences of the 33 class I tRNAs, for the remaining 18 amino acids, are presented here. These cover at least 44 codons out of a possible 49 codons for the 18 amino acids. Although these archaebacterial tRNAs follow general tRNA patterns, they are in detail distinct from both eucaryotic and eubacterial tRNAs. Moreover, the initiator tRNA is unique in having a 5'-triphosphorylated end.

Amino Acids↗
PubMedDate not supplied

[Comparative characteristics of the transport systems of C4-dicarboxylic acids in cultures of the genera Halobacterium and Halococcus].

The transport systems of the extreme halophilic organisms, Halobacterium and Halococcus, differ to a considerable degree in the kinetic parameters of succinate and fumarate transport, the exchange between exocellular and endocellular labeled dicarboxylates, and the rate at which labeled compounds in the cell are incorporated into cellular metabolism.

Biological Transport↗
PubMed1983

Phase-lifetime spectrophotometry of membranes from ion flux mutants of Halobacterium halobium.

Phase-lifetime spectrophotometry has been used to study the rate processes associated with intermediates in the photocycling pigments in membrane vesicles of mutant strains of Halobacterium halobium. Vesicles deficient in bacteriorhodopsin, but containing halorhodopsin, were monitored with light at 490 nm. Two relaxation processes, with kinetic parameters largely independent of pH over the range 6.2-7.8, were found to be associated with halorhodopsin photocycling in 4 M NaCl, 10 mM buffer at 23 degrees C. The average relaxation times are 0.94 and 11.4 ms. When vesicles deficient in both bacteriorhodopsin and halorhodopsin were monitored at 370 nm, a single relaxation process with an average relaxation time of 168 ms was detected. This process is independent of pH over the range 4.7-8.8. Examination of vesicles from ion flux mutants showed this slow process to be unrelated to halorhodopsin content and to derive from another photoreactive retinal pigment, possibly the recently described slow cycling pigment s-rhodopsin.

Bacteriorhodopsins↗
PubMed1982

Reconstitution of bacteriorhodopsin vesicles with Halobacterium halobium lipids. Effects of variations in lipid composition.

Reconstitution of bacteriorhodopsin into vesicles has been studied using individual and defined mixtures of fractionated Halobacterium halobium polar lipids. The lipids varied greatly in their ability to form vesicles that translocated protons and showed stimulation by valinomycin. Thus, phosphatidylglycerol phosphate gave mainly lipid-protein aggregates, while glycolipid sulfate gave mainly functional vesicles. Addition of glycolipid sulfate to phosphatidylglycerol phosphate promoted vesicle formation. Reconstitutions performed with different combinations of the purified lipids showed: 1) that vesicles with maximal proton pumping are obtained with a mixture of phosphatidylglycerol phosphate and glycolipid sulfate at a ratio close to that found in the purple membrane; 2) increasing the concentration of glycolipid sulfate in vesicles increases the stimulation of proton translocation by valinomycin; 3) phosphatidylglycerol sulfate cannot replace glycolipid sulfate or phosphatidylglycerol phosphate, and 4) vesicles containing sulfated polar lipids only are inferior to those in which liquid combinations containing phosphatidylglycerol phosphate are used.

Bacteriorhodopsins↗
PubMed1982

[Light-induced changes in quantum yields of the photochemical cycle of conversion of bacteriorhodopsin and transmembrane proton transfer in cells of Halobacterium halobium].

It was found that the rate of proton efflux from the cells, vH+, and the turnover number of bacteriorhodopsin photoconversion cycle per second, vM, are gradually decreased during continuous illumination of Halobacterium halobium with orange light (550-650 nm, 10(3) W/m2). The steady-state value of vH+ after 3 min of illumination is 3 times lower than vH+ at the 1st second of illumination. At the same time the concentration of the photochemical cycle intermediate, M412, the quantum yield of its formation, phi M, and the quantum efficiency of proton efflux, phi H+, are decreased (phi M and phi H+ up to 3-4-fold), whereas the concentration of the initial form of bacteriorhodopsin, BR570, and lifetime of M412, tau, are increased. These light-induced effects are abolished by uncoupler, carbonylcyanide m-chlorophenylhydrazone (CCCP) and are enhanced by the phosphorylation inhibitor, N,N'-dicyclohexylcarbodiimide (DCCD). This suggests that the observed changes of M412 and BR570 concentrations, tau, VH+, VM, phi M and phi H+ are due to the light-induced changes in the transmembrane electric potential, delta psi, and in pH inside and outside the cell, which control the photochemical cycle reactions. The decrease of phi M and phi H+ is discussed on the basis of an earlier proposed scheme of the branched photochemical cycle. It is assumed that the back reactions of the cycle (shunts) not coupled with the transmembrane proton translocation, e.g. conversion of L550 (P550) into BR570 without M412 formation, etc., become more probably at high values of the proton electrochemical potential gradient.

Bacteriorhodopsins↗
PubMedDate not supplied

[Inhibitory effect of blue and ultraviolet light on photoinduced changes in the pH of a suspension of Halobacterium halobium cells].

It was found that when switching on blue and UV light with the green one at the background decreased the acidification of Halobacterium suspension sensitized with bacterirhodopsin. Three facts are responsible for the acidification decrease. 1. At high intensity of the background green light (above 10(2)/Wt/m2) the effect predominates, which is conditioned by the action of blue light on the intermediate of the photochemical cycle of bacteriorhodopsin P419 (M412). Phototransformation of the latter prevents the transmembrane transfer of H+. 2. At high intensities of shortwave light (10(3)Wt/m2) alkalization of the suspension sensitized with unidentified pigment is observed. 3. At low intensities of blue and UV light (10 Wt/m2) the effect with the maximum in the action spectrum at 390 nm predominates. It is increased after preillumination of Halobacteria with green light and after short-term incubation (to 1-2 hours at 20 degrees C) of the cells with dicyclohexylcarbodiimide. It is inhibited with dinitrophenol. The effect is suggested to result from the photo-induced increase of cell membrane permeability for H+. Judging by the action spectrum it may be involved in the phototaxis of Halobacteria.

Bacteriorhodopsins↗
PubMed1980

Action spectra determined with tunable dye laser light for light-induced proton efflux and uptake in membrane vesicles of Halobacterium halobium.

A new pigment from Halobacterium halobium has been previously described which mediates the electrogenic extrusion of sodium ions when illuminated. Using essentially monochromatic light (0.05 nm bandwidth), maximum activity for this pigment occurred at 590 nm as monitored by passive proton uptake in envelope vesicles. The uncoupler bis(hexafluoroacetonyl)-acetone did not shift peak activity, but did increase passive proton influx. When the new pigment (NaP590) bacteriorhodopsin, the well characterized proton pump, and were compared at their respective wave-lengths of maximum activity, NaP590 required approximately 100-fold more energy to achieve saturation.

Acetone↗
PubMed1994

Kinetic mechanism of Halobacterium halobium Mn(2+)-activated alkaline phosphatase.

The extreme halophilic archaebacterium Halobacterium halobium contains an atypical alkaline phosphatase which is selectively activated by Mn2+ ions (Bonet et al., 1991: Int. J. Biochem. 23, 1445-1451). Enzyme kinetic mechanism in the presence of Mn2+ with p-nitrophenylphosphate as substrate was analysed by initial rate and product and competitive inhibition studies. The results indicate that there is an ordered addition of activator and substrate, Mn2+ being first in binding to the phosphatase, and that inorganic phosphate is the last product in leaving the enzyme active site. Strong inhibition by vanadate suggests that a phosphoenzyme intermediate is formed during enzymatic phosphohydrolysis of substrate.

Alkaline Phosphatase↗
PubMed1994

Calorimetric investigation of the NABH4-modified bacteriorhodopsin in purple membrane from Halobacterium halobium.

Comparative differential scanning calorimetric study of intact purple membranes from Halobacterium halobium and when 50% of bacteriorhodopsin molecules were cut off by NaBH4 in the dark shows that two peaks beneath the overall endotherms correspond to a process of bacteriorhodopsin denaturation. These results suggest a different structural organization of two populations of bacteriorhodopsin in intact dark-adapted purple membranes.

Bacteriorhodopsins↗
PubMed1994

Identification of volatile forms of methyl groups released by Halobacterium salinarium.

halobacterium salinarium (formerly H. halobium) is a chemotactic and phototactic archaeon from which volatile methyl groups are released continually, a phenomenon related to its sensory system. We found that released methyl groups comprised two different chemical species, methanol and methanethiol, the sulfur analog of methanol. Radiolabeling experiments showed that the methyl groups of both compounds, as well as the sulfur of methanethiol, were derived from methionine but were donated to cellular components and subsequently cleaved to produce the respective volatile compounds. Previous work had shown that chemostimuli and photostimuli result in transient increases in the rate of release of volatile methyl groups. We found that these increases reflected increased release of methanol but not of methanethiol. Thus, the methyl group chemistry of the H. salinarium sensory system is analogous to the well-studied chemotactic system of Escherichia coli. The reactions that result in methanethiol release are of unknown function and have unusual features. They may involve a methionine-gamma-lyase activity we detected in H. salinarium. Sulfur derived from methionine was found attached to specific proteins in reduction-sensitive disulfide linkages.

Carbon-Sulfur Lyases↗
PubMed1977

Structural studies on Halobacterium halobium bacteriorhodopsin.

Bacteriorhodopsin, isolated from Halobacterium halobium, is an intrinsic membrane protein containing covalently attached retinal and driven by a cyclic light-driven protonmotive force. In order to extend three-dimensional analyses already in progress and to define the covalent features of such proteins, the determination of the primary structure of bacteriorhodopsin has been initiated, using techniques that can be applied to the sequence analyses of other intrinsic membrane proteins as well. The amino acid composition of bacteriorhodopsin prepared by new procedures compares well to that previously published. Various delipidation procedures have been examined for their effectiveness in yielding protein in a physical state that is susceptible to fragmentation by a number of chemical and proteolytic agents. Organic extraction, particularly in acetone:ammonium hydroxide, has proved most useful. Detergent extraction was effective in delipidating but rendered the protein inert to attack by various cleavage reagents. Sequence information was obtained from fragments isolated from several hydrolytic preparations of low percent cleavage. The most complete fragmentation was obtained from hydrolysis of bacteriorhodopsin previously modified with succinic or maleic anhydride. Both solubility and fragmentation susceptibility were enhanced by these reactions and several other derivatives of bacteriorhodopsin are currently being investigated. The behavior of bacteriorhodopsin under the conditions examined, as well as the sequence information obtained, suggest that bacteriorhodopsin is mostly contained within the lipid milieu of the membrane and may represent a class of membrane proteins that do not contain appreciable hydrophilic domains.

Amino Acids↗