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At least 19 recordsLinked to original sources
PubMed1972

Studies on Chloroplast Development and Replication in Euglena: III. A Study of the Site of Synthesis of Alkaline Deoxyribonuclease Induced during Chloroplast Development in Euglena gracilis.

During chloroplast development in Euglena, the activity of a specific DNase, Euglena alkaline DNase, increases in a manner similar to that of chlorophyll synthesis, but without the lag customarily associated with the early hours of chlorophyll synthesis. The increase in Euglena alkaline DNase activity is not inhibited by chloramphenicol or by streptomycin, but is inhibited by cycloheximide. Euglena alkaline DNase activity is present in a group of aplastidic substrains which contain carotenoids. These results are interpreted to mean that this chloroplast-related DNase is synthesized in the cytoplasm, and that the genetic information for this enzyme is probably nuclear.It is also shown that different bleached substrains exhibit substantial variation, both in total carotenoids and in Euglena alkaline DNase activity. These results are discussed in terms of the possibility that a cytoplasmic photoreceptor system is influencing the light-induced increase in Euglena alkaline DNase activity.

Journal Article↗
PubMed1989

Isolation and characterisation of a cDNA clone for a chlorophyll synthesis enzyme from Euglena gracilis. The chloroplast enzyme hydroxymethylbilane synthase (porphobilinogen deaminase) is synthesised with a very long transit peptide in Euglena.

A cDNA expression library was constructed from light-grown Euglena gracilis poly(A)-rich RNA in lambda gt11. Antibodies to Euglena hydroxymethylbilane synthase, the third enzyme in the porphyrin biosynthetic pathway, were used to screen the library and a clone encoding part of the sequence of hydroxymethylbilane synthase was identified. This was used to rescreen the library and a full-length clone was isolated, which encoded not only the entire mature protein (Mr 36,927), but also an N-terminal extension of 139 amino acids. The deduced Mr of the whole polypeptide is 51,744, which corresponds to the size of the protein immunoprecipitated from the translation products of Euglena poly(A)-rich RNA. The mature protein is 60-70% similar to hydroxymethylbilane synthase from human erythrocytes and Escherichia coli. The sequence of the N-terminal extension has similarities to both the transit peptides of chloroplast proteins and those for the endoplasmic reticulum. This is the first report both of a cDNA clone for an enzyme of the chlorophyll biosynthetic pathway and of a putative transit peptide for a nuclear-encoded Euglena protein.

Amino Acid Sequence↗
PubMed1997

Two new group-II twintrons in the Euglena gracilis chloroplast are absent in basally branching Euglena species.

Studies of the phylogeny and chloroplast intron content of selected Euglena species have led to insights in our understanding of the timing of intron acquisition. In the current study, two new twintrons, found in E. gracilis, have been characterized by the analysis of partially spliced pre-mRNAs. Intron 1 of atpE is a 463-nt group-II intron interrupted by a second group-II intron 320 nt long. Intron 1 of psbD is also a group-II twintron with external and internal introns of 635 nt and 463 nt, respectively. The two introns composing the psbD twintron, as well as six additional group-II introns found in the E. gracilispsbD gene, are not present in several basally branching Euglena species, including E. myxocylindracea, E. stellata and E. viridis. The distribution of psbD introns in Euglena is consistent with a late evolutionary acquisition of group-II introns in this lineage.

Animals↗
PubMed1992

Microsomal ethanol-oxidizing system in Euglena gracilis. Similarities between Euglena and mammalian cell systems.

1. ADH activity of Euglena grown with 50 mM ethanol decreased, but MEOS activity increased with a corresponding increase in the total amount of cytochrome P-450. 2. Phenobarbital treatment increased the total amount of cytochrome P-450. 3. CO and KCN, cytochrome P-450 ligands, diminished acetaldehyde formed from ethanol oxidation by MEOS. 4. The amounts of NAD(P)H cytochrome c reductases and cytochrome b5 type, components of microsomal monooxygenase reaction, have been spectrophotometrically measured. 5. NAD(P)H cytochrome c reductases activities were induced by phenobarbital. 6. DMSO, an inhibitor of rabbit MEOS, inhibited O2 consumption (11-20%) by Euglena grown with an ethanol, but not a lactate medium. 7. These studies indicate the presence of cytochrome P-450-dependent MEOS in Euglena similar to that in the mammalian hepatic cell.

Alcohol Dehydrogenase↗
PubMed2004

The origin of photoactivated adenylyl cyclase (PAC), the Euglena blue-light receptor: phylogenetic analysis of orthologues of PAC subunits from several euglenoids and trypanosome-type adenylyl cyclases from Euglena gracilis.

Photoactivated adenylyl cyclase (PAC) is the blue-light receptor flavoprotein recently identified as a photoreceptor for photoavoidance of the unicellular flagellate, Euglena gracilis. To gain an insight into the evolution of this unique protein, similar sequences were searched for in several euglenoids by reverse transcriptase-polymerase chain reaction (RT-PCR) using degenerate primers. Two similar transcripts were detected in each of the four phototrophic euglenoids, Euglena stellata, Colacium sideropus, Eutreptia viridis, Eutreptiella gymnastica, and in an osmotrophic (i.e., obtaining nutrients by absorption) one, Khawkinea quartana, but not in a phagotrophic euglenoid, Petalomonas cantuscygni. Each of them seemed to be orthologous to PACalpha and PACbeta, respectively, and had the same domain structure as PAC subunits each of which is composed of two flavin binding domains, F1 and F2, each followed by an adenylyl cyclase catalytic domain, C1 and C2, respectively. This fact implies that they constitute a functional photoactivated adenylyl cyclase like PAC. Phylogenetic analysis of the adenylyl cyclase catalytic domains revealed that they belong to a bacterial cluster, not to a trypanosomal one. In addition, two trypanosome-type adenylyl cyclases were discovered in E. gracilis. In contrast to PAC, deduced amino acid sequences of the trypanosome-type adenylyl cyclases indicated that they are integral membrane proteins with a membrane spanning region at the midpoint of them, followed by an adenylyl cyclase catalytic domain which seems cytoplasmic. Overall, we propose that PAC might have been transferred to euglenoids on the occasion of secondary endosymbiosis.

Adenylyl Cyclases↗
PubMed1981

The nucleotide sequence of Euglena cytoplasmic phenylalanine transfer RNA. Evidence for possible classifications of Euglena among the animal rather than the plant kingdom.

The nucleotide sequence of cytoplasmic phenylalanine tRNA from Euglena gracilis has been elucidated using procedures described previously for the corresponding chloroplastic tRNA [Cell, 9, 717 (1976)]. The sequence is: pG-C-C-G-A-C-U-U-A-m(2)G-C-U-Cm-A-G-D-D-G-G-G-A-G-A-G-C-m(2)2G-psi-psi-A-G-A-Cm -U-Gm-A-A-Y-A-psi-C-U-A-A-A-G-m(7)G-U-C-*C-C-U-G-G-T-psi-C-G-m(1)A-U-C-C-C-G-G- G-A-G-psi-C-G-G-C-A-C-C-A. Like other tRNA Phes thus far sequenced, this tRNA has a chain length of 76 nucleotides. The sequence of E. gracilis cytoplasmic tRNA Phe is quite different (27 nucleotides out of 76 different) from that of the corresponding chloroplastic tRNA but is surprisingly similar (72 out of 76 nucleotides identical) to that of tRNA Phe from mammalian cytoplasm. This extent of sequence homology even exceeds that found between E. gracilis and wheat germ cytoplasmic tRNA Phe. These findings raise interesting questions on the evolution of tRNAs and the taxonomy of Euglena.

Animals↗
PubMed1971

Activities of various cobalamins for Euglena gracilis with reference to vitamin B 12 assay with Euglena.

Coenzyme B(12) and methylcobalamin in water are less active in promoting growth of Euglena gracilis Z strain than the same concentrations of cyanocobalamin and hydroxocobalamin which are equally active. When bound to human serum or human liver homogenate, however, the activities of these four cobalamins do not differ significantly with one exception. The results suggest that the Euglena assay using cyanocobalamin standards is not satisfactory for quantitation of coenzyme B(12) and methylcobalamin in water but acceptable when coenzyme B(12) and methylcobalamin are bound to serum or liver. Sulphitocobalamin in water is as active as cyanocobalamin and hydroxocobalamin but nitritocobalamin is less active. Factor B, the monocarboxylic acids of cyanocobalamin and hydroxocobalamin, and the dicarboxylic acid of cyanocobalamin in water were inactive.

Biological Assay↗
PubMed2004

Isolation and characterization of oxygen-evolving photosystem II complexes retaining the PsbO, P and Q proteins from Euglena gracilis.

Oxygen-evolving photosystem II (PSII) complexes of Euglena gracilis were isolated and characterized. (1) The PSII complexes contained three extrinsic proteins of 33 kDa (PsbO), 23 kDa (PsbP) and 17 kDa (PsbQ), and showed oxygen-evolving activity of around 700 micromol O2 (mg Chl)(-1) h(-1) even in the absence of Cl- and Ca2+ ions. (2) NaCl-treatment removed not only PsbP and PsbQ but also a part of PsbO from Euglena PSII, indicating that PsbO binds to Euglena PSII more loosely than those of other organisms. Treatments by urea/NaCl, alkaline Tris or CaCl2 completely removed the three extrinsic proteins from Euglena PSII. (3) Each of the Euglena extrinsic proteins bound directly to PSII independent of the other extrinsic proteins, which is similar to the binding properties of the extrinsic proteins in a green alga, Chlamydomonas reinhardtii. (4) One of the significant features of Euglena PSII is that the oxygen evolution was not enhanced by Ca2+. When CaCl2-treated Euglena PSII was reconstituted with PsbO, the oxygen-evolving activity was stimulated by the addition of NaCl, but no further stimulation was observed by CaCl2. (5) Oxygen evolution of Euglena PSII reconstituted with PsbO from C. reinhardtii or spinach instead of that from Euglena also showed no enhancement by Ca2+, whereas a significant enhancement of oxygen evolution was observed by Ca2+ when the green algal or higher plant PSII was reconstituted with Euglena PsbO instead of their own PsbO. These results indicate that the PSII intrinsic proteins instead of the extrinsic PsbO protein, are responsible for the stimulation of oxygen evolution by Ca2+. Sequence comparison of major PSII intrinsic proteins revealed that PsbI of Euglena PSII is remarkably different from other organisms in that Euglena PsbI possesses extra 16-17 residues exposed to the luminal side. This may be related to the loss of enhancement of oxygen evolution by Ca2+ ion.

Algal Proteins↗
PubMed2005

Homologous and heterologous reconstitution of Golgi to chloroplast transport and protein import into the complex chloroplasts of Euglena.

Euglena complex chloroplasts evolved through secondary endosymbiosis between a phagotrophic trypanosome host and eukaryotic algal endosymbiont. Cytoplasmically synthesized chloroplast proteins are transported in vesicles as integral membrane proteins from the ER to the Golgi apparatus to the Euglena chloroplast. Euglena chloroplast preprotein pre-sequences contain a functional N-terminal ER-targeting signal peptide and a domain having characteristics of a higher plant chloroplast targeting transit peptide, which contains a hydrophobic stop-transfer membrane anchor sequence that anchors the precursor in the vesicle membrane. Pulse-chase subcellular fractionation studies showed that (35)S-labeled precursor to the light harvesting chlorophyll a/b binding protein accumulated in the Golgi apparatus of Euglena incubated at 15 degrees C and transport to the chloroplast resumed after transfer to 26 degrees C. Transport of the (35)S-labeled precursor to the chlorophyll a/b binding protein from Euglena Golgi membranes to Euglena chloroplasts and import into chloroplasts was reconstituted using Golgi membranes isolated from 15 degrees C cells returned to 26 degrees C. Transport was dependent upon extra- and intrachloroplast ATP and GTP hydrolysis. Golgi to chloroplast transport was not inhibited by N-ethylmaleimide indicating that fusion of Golgi vesicles to the chloroplast envelope does not require N-ethylmaleimide-sensitive factor (NSF). This suggests that N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) are not utilized in the targeting fusion reaction. The Euglena precursor to the chloroplast-localized small subunit of ribulose-1,5-bisphosphate carboxylase was not imported into isolated pea chloroplasts. A precursor with the N-terminal signal peptide deleted was imported, indicating that the Euglena pre-sequence has a transit peptide that functions in pea chloroplasts. A precursor to the small subunit of ribulose-1,5-bisphosphate carboxylase with the hydrophobic membrane anchor and the pre-sequence region C-terminal to the hydrophobic membrane anchor deleted was imported localizing the functional transit peptide to the Euglena pre-sequence region between the signal peptidase cleavage site and the hydrophobic membrane anchor. The Euglena precursor to the small subunit of ribulose-1,5-bisphosphate carboxylase and the deletion constructs were not post-translationally imported into isolated Euglena chloroplasts indicating that vesicular transport is the obligate import mechanism. Taken together, these studies suggest that protein import into complex Euglena chloroplasts evolved by developing a novel vesicle fusion targeting system to link the host secretory system to the transit peptide-dependent chloroplast protein import system of the endosymbiont.

Adenosine Triphosphate↗
PubMed2002

Identification and comparative analysis of the chloroplast alpha-subunit gene of DNA-dependent RNA polymerase from seven Euglena species.

When the sequence of the Euglena gracilis chloroplast genome was reported in 1993 the alpha-subunit gene (rpoA) of RNA polymerase appeared to be missing, based on a comparison of all putative reading frames to the then known rpoA loci. Since there has been a large increase in known rpoA sequences, the question of a Euglena chloroplast rpoA gene was re-examined. A previously described unknown reading frame of 161 codons was found to be part of an rpoA gene split by a single group III intron. This rpoA gene, which is highly variable from species to species, was then isolated and characterized in five other euglenoid species, Euglena anabaena, Euglena granulata, Euglena myxocylindracea, Euglena stellata and Euglena viridis, and in the Astasia longa plastid genome. All seven Euglena rpoA genes have either one or three group III introns. The rpoA gene products in Euglena spp. appear to be the most variable in this gene family when compared to the rpoA gene in other species of bacteria, algae and plants. Additionally, Euglena rpoA proteins lack a C-terminal domain required for interaction with some regulatory proteins, a feature shared only with some chlorophyte green algae. The E.gracilis rpoA gene is the distal cistron of a multigene cluster that includes genes for carbohydrate biosynthesis, photosynthetic electron transport, an antenna complex and ribosomal proteins. This study provides new insights into the transcription system of euglenoid plastids, the organization of the plastid genome, group III intron evolution and euglenoid phylogeny.

Amino Acid Sequence↗
PubMed1995

Evidence for the late origin of introns in chloroplast genes from an evolutionary analysis of the genus Euglena.

The origin of present day introns is a subject of spirited debate. Any intron evolution theory must account for not only nuclear spliceosomal introns but also their antecedents. The evolution of group II introns is fundamental to this debate, since group II introns are the proposed progenitors of nuclear spliceosomal introns and are found in ancient genes from modern organisms. We have studied the evolution of chloroplast introns and twintrons (introns within introns) in the genus Euglena. Our hypothesis is that Euglena chloroplast introns arose late in the evolution of this lineage and that twintrons were formed by the insertion of one or more introns into existing introns. In the present study we find that 22 out of 26 introns surveyed in six different photosynthesis-related genes from the plastid DNA of Euglena gracilis are not present in one or more basally branching Euglena spp. These results are supportive of a late origin for Euglena chloroplast group II introns. The psbT gene in Euglena viridis, a basally branching Euglena species, contains a single intron in the identical position to a psbT twintron from E.gracilis, a derived species. The E.viridis intron, when compared with 99 other Euglena group II introns, is most similar to the external intron of the E.gracilis psbT twintron. Based on these data, the addition of introns to the ancestral psbT intron in the common ancester of E.viridis and E.gracilis gave rise to the psbT twintron in E.gracilis.

Animals↗