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At least 1,423 records · Page 79Linked to original sources
PubMed1991

An hsp70 homolog is encoded on the plastid genome of the red alga, Porphyra umbilicalis.

A PCR experiment using Porphyra umbilicalis DNA as the template and degenerate oligonucleotides representing conserved regions of hsp70 amino acid sequences generated a 1 kb product that hybridized exclusively to the plastid DNA of this red alga. DNA sequencing of two contiguous EcoRI plastid DNA clones revealed a 620 amino acid open reading frame with 71% identity to the dnaK gene of the cyanobacterium, Synechocystis 6803. Northern hybridization experiments detected a 2.3 kb transcript that is present in control (15 degrees C) cultures and increases approximately 7-fold upon heat shock (75 minutes at 30 degrees C).

Amino Acid Sequence↗
PubMed1992

Characterisation of a chloroplast-encoded secY homologue and atpH from a chromophytic alga. Evidence for a novel chloroplast genome organisation.

secY is a prokaryotic gene that encodes the SecY protein, an integral membrane component of the prokaryotic protein translocation apparatus. A chloroplast-encoded secY homologue has been identified in the unicellular, chromophytic alga, Pavlova lutherii. The gene predicts a protein composed of ten membrane-spanning regions, that is approximately 25% homologous and 50% similar to bacterial and plastid SecY proteins. The secY gene from P. lutherii is independent of the ribosomal protein (rp) gene cluster to which it is closely linked in other organisms. In P. lutherii secY is located 5' to atpI and atpH. Since, in higher plants the atpIHFA gene cluster and the rp gene cluster are separated by approximately 50 kb, we conclude, this indicates a novel chloroplast gene arrangement in P. lutherii.

Amino Acid Sequence↗
PubMed1992

H(+)-translocating ATPase and Na+/H+ antiport activities in the plasma membrane of the marine alga Platymonas viridis.

Proton transport by the vanadate-sensitive ATPase in plasma membrane (PM) vesicles from the marine unicellular microalga Platymonas viridis was investigated. The ATP-dependent generation of delta pH across the membranes of PM vesicles was followed by the changes in the absorbance of the aminoacridine probe, Acridine orange. Na+ caused the decay of delta pH generated by the ATPase, the rate of the decay being dependent on the concentrations of Na+ added. The phenomenon was specific for Na+. Amiloride inhibited Na(+)-dependent delta pH decay. The experiments support the idea of a Na(+)-extruding mechanism (H(+)-translocating ATPase plus Na+/H+ antiporter) operating in the PM of marine alga Pl. viridis.

Adenosine Triphosphate↗
PubMed1992

Receptor mediated mineralocorticoid action in alga cell mutants.

The multiplication of Chlamydomonas cells can be arrested by the spirolactone derivative RU 26752 and this is fully reversible by the natural hormone aldosterone. Continuous growth in the presence of RU 26752 led to the isolation of a population subsequently resistant to the action of mineralocortoid analogues, due possibly to the selection of mutant cells. Immunophotochemical evidence is provided for a 52 kDa protein that possesses functional steroid and DNA binding domains. Alga cells therefore appear to respond to steroid hormones in a manner similar to the mammalian systems, possibly via a receptor that may represent a pygmy ancestor of the latter day steroid receptor superfamily.

Animals↗
PubMed1993

Characterization and purification of a hydrogenase from the eukaryotic green alga Scenedesmus obliquus.

Several catalytic properties of the hydrogenase from Scenedesmus obliquus have been examined to optimize the purification conditions. The Km-value for H2-evolution in the presence of the most effective electron mediator methylviologen is 0.66 mM. The pH-optimum is 6.3, the temperature-optimum is 50 degrees C and the energy of activation is 38.4 +/- 2 kJ.mol-1. The soluble hydrogenase from the green alga, Scenedesmus obliquus, was purified 1290-fold to homogeneity. The enzyme consists of two subunits with molecular masses of 55 kDa and 36 kDa. The molecular weight of the native enzyme, determined by gel filtration, is 150 +/- 5 kDa.

Chlorophyta↗
PubMed1995

Internodal cells of the giant green alga Chara as an expression system for ion channels.

Internodal cells of the giant green alga Chara corallina were utilized as an expression system for two nicotinic acetylcholine receptor subtypes (nAChR) derived from rat muscle. From Chara internodes that were pressure-injected with the respective cRNA, cytoplasmic droplets were formed, and functional expression of channel proteins in the membrane delineating the droplets was confirmed by patch-clamp techniques. The droplet membrane was recently identified as the original tonoplast, patch-clamp recordings on cytoplasmic droplets were easily performed and single channel activity could be measured with high resolution. The properties of the recombinant nAChR observed in this membrane were similar to those reported for the channel expressed in Xenopus oocytes, and for the native channel recorded in situ. The Chara expression system is, therefore, suitable for functional expression of animal messenger RNAs, without the risk of signal contamination by intrinsic ion channels. It offers a low-cost and practical alternative to the use of Xenopus oocytes for the investigation of heterologously expressed ion channels.

Animals↗
PubMed1995

Solubilization and purification of aldehyde-generating fatty acyl-CoA reductase from green alga Botryococcus braunii.

Membrane-bound fatty acyl-CoA reductase from the green alga Botryococcus braunii has been solubilized from the microsomal preparation by 0.1% octyl beta-glucoside and purified to near homogeneity by Blue A agarose and palmitoyl-CoA agarose affinity column chromatography. The molecular mass of the enzyme was estimated by SDS-PAGE to be 35 kDa. The enzyme generates fatty aldehyde by reduction of fatty acyl-CoA with NADH as the reductant. The N-terminal amino acid sequence of this protein that represents the first eucaryotic aldehyde-generating reductase to be purified shows high homology with the N-terminus of fatty acid reductase from bacteria.

Aldehyde Oxidoreductases↗
PubMed1996

NMR structures of a mitochondrial transit peptide from the green alga Chlamydomonas reinhardtii.

The 26-amino-acid pre-sequence of the ATP synthase beta subunit that directs the protein from the cytosol to mitochondria in the unicellular green alga Chlamydomonas reinhardtii has been synthesised and analysed using NMR spectroscopy/circular dichroism and compared to a chloroplast transit peptide from the same organism. The results demonstrate that the peptide, though mainly unstructured in water, undergoes a strong conformational change in a 36% water/64% 2,2,2-trifluoroethanol mixture. In this solvent condition, an alpha-helix was characterised by NMR from residue 2 to 26. Structure calculations under NMR restraints lead to a population of models of which 60% are kinked at position 9-10. Structural analysis indicates two hydrophobic sectors on the models with a discontinuity at the 9-10 kink level. The structures suggest a different interaction mode with the mitochondrial membrane compared to the chloroplast transit peptide.

Amino Acid Sequence↗
PubMed1983

Preliminary crystallographic data for plastocyanins from an alga (Enteromorpha prolifera) and from cucumber (Cucumis sativus).

The plastocyanins from a green alga (Enteromorpha prolifera) and cucumber (Cucumis sativus) have been crystallized. Crystal data are as follows: E. prolifera plastocyanin, space group I4, a = b = 53.9 A, c = 59.4 A, Z = 8; C. sativus plastocyanin, space group P4(1) (or P4(3) ), a = b = 66.7 A, c = 46.0 A, Z = 8. Accordingly, the asymmetric units of the crystals contain one and two molecules, respectively.

Chlorophyta↗
PubMed1990

Crystal structure of plastocyanin from a green alga, Enteromorpha prolifera.

The crystal structure of the Cu-containing protein plastocyanin (Mr 10,500) from the green alga Enteromorpha prolifera has been solved by molecular replacement. The structure was refined by constrained-restrained and restrained reciprocal space least-squares techniques. The refined model includes 111 solvent sites. There is evidence for alternate conformers at eight residues. The residual is 0.12 for a data set comprising 74% of all observations accessible at 1.85 A resolution. The beta-sandwich structure of the algal plastocyanin is effectively the same as that of poplar leaf (Populus nigra var. italica) plastocyanin determined at 1.6 A resolution. The sequence homology between the two proteins is 56%. Differences between the contacts in the hydrophobic core create some significant (0.5 to 1.2 A) movements of the polypeptide backbone, resulting in small differences between the orientations and separations of corresponding beta-strands. These differences are most pronounced at the end of the molecule remote from the Cu site. The largest structural differences occur in the single non-beta strand, which includes the sole turn of helix in the molecule: two of the residues in a prominent kink of the poplar plastocyanin backbone are missing from the algal plastocyanin sequence, and there is a significant change in the position of the helical segment in relation to the beta-sandwich. Several other small but significant structural differences can be correlated with intermolecular contacts in the crystals. An intramolecular carboxyl-carboxylate hydrogen bond in the algal plastocyanin may be associated with an unusually high pKa. The dimensions of the Cu site in the two plastocyanins are, within the limits of precision, identical.

Amino Acid Sequence↗
PubMed1992

Large ATP synthase operon of the red alga Antithamnion sp. resembles the corresponding operon in cyanobacteria.

The large plastid ATP synthase operon of the multicellular red alga Antithamnion sp. was cloned and the sequence of six ATPase genes determined. The operon resembles more the one from cyanobacteria than the ATP synthase operon of the chloroplast genome. The gene order is atpI, H, G, F, D and A, coding for the ATPase subunits a, c, b', b, delta and alpha, respectively. In green plants, the genes atpG and atpD are located in the nucleus. Unlike the situation in three published cyanobacterial ATP synthase operons, atpC, coding for the gamma subunit, is not a part of the rhodoplast operon. A single 4.5 kb transcript was detected with atpG, F, D and A gene probes that could span the whole operon, but no transcript could be detected with atpI and atpH probes. The end of an open reading frame preceding the atp genes shows remarkable homology to elongation factor TS from Escherichia coli. Behind the ATPase cluster, two open reading frames were detected that are not homologous to any known chloroplast gene. One of them may code for a transport protein of unknown specificity. Gene arrangement and sequence comparisons support the hypothesis of a polyphyletic origin of rhodoplasts and chloroplasts.

Amino Acid Sequence↗
PubMed1992

Crystal structure of oxidized flavodoxin from a red alga Chondrus crispus refined at 1.8 A resolution. Description of the flavin mononucleotide binding site.

In order to describe the detailed conformation of the oxidized flavodoxin from a eukaryotic red alga, Chondrus crispus, the crystal structure has been refined by a restrained least-squares method. The crystallographic R factor is 0.168 for 13,899 reflections with F greater than 2 sigma F between 6.0 and 1.8 A resolution. The refined model includes 173 amino acid residues, flavin mononucleotide (FMN) and 110 water molecules. The root-mean-square deviation in bond lengths from ideal values is 0.015 A, and the mean co-ordinate error is estimated to be 0.2 A. The FMN is located at the periphery of the molecule. The orientation of the isoalloxazine ring is such that the C-7 and C-8 methyl groups are exposed to solvent and the pyrimidine moiety is buried in the protein. Three peptide segments, T8-T13, T55-T58 and D94-C103, are involved in FMN binding. The first segment of T8-T13 enfolds the phosphate group of the FMN. The three oxygen atoms in the phosphate group form extensive hydrogen bonds with amide groups of the main chain and the O gamma atoms of the side-chains in this segment. T55 O and W56 N epsilon 1 in the second segment form hydrogen bonds with O-2 in the ribityl moiety and one of the oxygen atoms in the phosphate group, respectively. The O gamma H of T58 forms a hydrogen bond with the N-5 atom in the isoalloxazine ring, which is expected to be protonated in the semiquinone form. The third segment is in contact with the isoalloxazine ring. It appears that the hydrogen bond acceptor of the NH of Asp94 in the third segment is O-2 rather than N-1 in the isoalloxazine ring. The isoalloxazine ring is flanked by the side-chains of Trp56 and Tyr98; it forms an angle of 38 degrees with the indole ring of Trp56 and is almost parallel to the benzene ring of Tyr98. The environment of the phosphate group is conserved as in other flavodoxins whereas that of the isoalloxazine ring differs. The relationship between the hydrogen bond to the N-5 in the ring and the redox potential for the oxidized/semiquinone couple is discussed.

Amino Acid Sequence↗
PubMed1992

Isolation, crystallization, crystal structure analysis and refinement of B-phycoerythrin from the red alga Porphyridium sordidum at 2.2 A resolution.

The light-harvesting pigment-protein complex B-phycoerythrin from the red alga Porphyridium sordidum has been isolated and crystallized. B-Phycoerythrin consists of three different subunits forming an (alpha beta)6 gamma aggregate. The three-dimensional structure of the (alpha beta)6 hexamer was solved by Patterson search techniques using the molecular model of C-phycocyanin from Fremyella diplosiphon. The asymmetric unit of the crystal cell (space group P3, with a = b = 111.2 A, c = 59.9 A, alpha = beta = 90 degrees, gamma = 120 degrees) contains two (alpha beta) monomers related by a local dyad. Three asymmetric units are arranged around the crystallographic 3-fold axis building an (alpha beta)6 hexamer, as in C-phycocyanin. The crystal structure has been refined by energy-restrained crystallographic refinement and model building. The conventional R-factor of the final model was 18.9% with data to 2.2 A resolution. The molecular structures of the alpha and beta-subunits resemble those of C-phycocyanin. Major changes in comparison to phycocyanin are caused by deletion or insertion of segments involved in protein-chromophore interactions. The singly linked phycoerythrobilin chromophores alpha-84, alpha-140a, beta-84 and beta-155 are each covalently bound to a cysteine by ring A. The doubly linked chromophore beta-50/beta-61 is attached at cysteine beta-50 through ring A and at cysteine beta-61 through ring D. B-Phycoerythrin contains additionally a 30 kDa gamma-subunit, which is presumably located in the central cavity of the hexamer. It is disordered, as a consequence of crystal and local symmetry averaging.

Amino Acid Sequence↗
PubMed1977

Isolation and characterization of chlorate-resistant mutants of the blue-green alga Nosoc muscorum.

Spontaneous chlorate-resistant (Clr) mutants of three classes were isolated from Nostoc muscorum under three different selective conditions. A Clr-N2 class of mutants lacked nitrate reductase and showed nitrate inhibition of nitrogen fixation. A Clr-NO3 group of het+ nif- mutants formed heterocysts, but lacked nitrogen fixation and active nitrogenase enzyme. The Clr-NO2 class included those mutants deficient in both active nitrogenase and nitrate reductase, as they were unable to grow at the expense of molecular nitrogen or with nitrate nitrogen. The results suggest a common genetic determinant of active nitrogenase and nitrate reductase in the blue-green alga N. muscorum.

Chlorates↗
PubMed1993

A diterpene epoxide from the marine brown alga Dictyota sp.: possible vasopressin V1 receptor antagonist.

A novel epoxide, in addition to eight known diterpenes, has been isolated from a marine brown alga of the genus Dictyota. The structures of these compounds were established by the interpretation and comparison of spectral data with literature data. Most of the isolates demonstrated vasopressin receptor antagonist activity in vitro with the new epoxide being the most active of the diterpenes tested.

Animals↗
PubMed1995

Cytotoxic metabolites from a fungal adherent of a marine alga.

Leptosins G, G1, G2 and H, belonging to a series of dimeric epipolythiodioxopiperazines, were isolated from the mycelium of a strain of Leptosphaeria sp. stuck on the marine alga Sargassum tortile. Their stereostructures were elucidated by chemical and spectral evidence.

Antineoplastic Agents↗
PubMed1995

Anti-tumour-promoting glyceroglycolipids from the green alga, Chlorella vulgaris.

Two new monogalactosyl diacylglycerols were isolated from the freshwater green alga, Chlorella vulgaris, as anti-tumour promoters, together with three monogalactosyl diacylglycerols and two digalactosyl diacylglycerols. The new monogalactosyl diacylglycerol containing (7Z,10Z)-hexadecadienoic acid showed a more potent inhibitory effect toward tumour promotion than the other glycerolipids isolated.

Anticarcinogenic Agents↗
PubMed1982

Isolation and characterization of four toxins from the blue-green alga, Microcystis aeruginosa.

Two alternative procedures for the isolation of toxins from the blue-green alga, Microcystis aeruginosa forma aeruginosa, are described. A novel approach is reported, whereby contaminating impurities are succinylated, exploiting the absence of free amino groups in toxin variants. All toxin variants comprise a hydrocarbon blocking group, five amino acid residues detectable by conventional means, while methylamine is liberated upon acid hydrolysis. Possible structural features are discussed relating to the observed chemical and physical properties of the toxins.

Amino Acids↗