JavaScript is NOT enabled !

* Show help

11 hits in Medvik Filters

Online article

The antenna-like domain of the cyanobacterial ferrochelatase can bind chlorophyll and carotenoids in an energy-dissipative configuration

Pazderník, Marek
Author Pazderník, Marek Institute of Microbiology, Czech Academy of Sciences, Centre Algatech, Třeboň, 379 81, Czech Republic. Faculty of Science, University of South Bohemia, České Budějovice 370 05, Czech Republic
Mareš, Jan
Author Mareš, Jan Institute of Microbiology, Czech Academy of Sciences, Centre Algatech, Třeboň, 379 81, Czech Republic. Faculty of Science, University of South Bohemia, České Budějovice 370 05, Czech Republic. Institute of Hydrobiology, Biology Centre of the Czech Academy of Sciences, České Budějovice 370 05, Czech Republic
Pilný, Jan
Author Pilný, Jan Institute of Microbiology, Czech Academy of Sciences, Centre Algatech, Třeboň, 379 81, Czech Republic
Sobotka, Roman
Author Sobotka, Roman Institute of Microbiology, Czech Academy of Sciences, Centre Algatech, Třeboň, 379 81, Czech Republic sobotka@alga.cz. Faculty of Science, University of South Bohemia, České Budějovice 370 05, Czech Republic

The Journal of biological chemistry. 2019 ; 294 (29) : 11131-11143. [pub] 20190605

J Biol Chem
ISSN 1083-351X
Medvik
Source

Ferrochelatase (FeCh) is an essential enzyme catalyzing the synthesis of heme. Interestingly, in cyanobacteria, algae, and plants, FeCh possesses a conserved transmembrane chlorophyll a/b binding (CAB) domain that resembles the first and the third helix of light-harvesting complexes, including a chlorophyll-binding motif. Whether the FeCh CAB domain also binds chlorophyll is unknown. Here, using biochemical and radiolabeled precursor experiments, we found that partially inhibited activity of FeCh in the cyanobacterium Synechocystis PCC 6803 leads to overproduction of chlorophyll molecules that accumulate in the thylakoid membrane and, together with carotenoids, bind to FeCh. We observed that pigments bound to purified FeCh are organized in an energy-dissipative conformation and further show that FeCh can exist in vivo as a monomer or a dimer depending on its own activity. However, pigmented FeCh was purified exclusively as a dimer. Separately expressed and purified FeCH CAB domain contained a pigment composition similar to that of full-length FeCh and retained its quenching properties. Phylogenetic analysis suggested that the CAB domain was acquired by a fusion between FeCh and a single-helix, high light-inducible protein early in the evolution of cyanobacteria. Following this fusion, the FeCh CAB domain with a functional chlorophyll-binding motif was retained in all currently known cyanobacterial genomes except for a single lineage of endosymbiotic cyanobacteria. Our findings indicate that FeCh from Synechocystis exists mostly as a pigment-free monomer in cells but can dimerize, in which case its CAB domain creates a functional pigment-binding segment organized in an energy-dissipating configuration.

MeSH
Chlorophyll A metabolism MeSH
Chlorophyll metabolism MeSH
Dimerization MeSH
Ferrochelatase chemistry metabolism MeSH
Phylogeny MeSH
Carotenoids metabolism MeSH
Protein Conformation MeSH
Light-Harvesting Protein Complexes metabolism MeSH
Synechocystis enzymology MeSH
Binding Sites MeSH
Publication type
Journal Article MeSH
Research Support, Non-U.S. Gov't MeSH

Online article

A novel mutation in the FECH gene in a Czech family with erythropoietic protoporphyria and a population study of IVS3-48C variant contributing to the disease

Folia biologica (Praha). 2015 ; 61 (6) : 227-232.

Folia biol. (Praha)
ISSN 0015-5500
Medvik
Source

Erythropoietic protoporphyria (EPP), a chronic erythropoietic porphyria, is characterized by excess accumulation of protoporphyrin, particularly in erythroid cells. EPP inheritance is complex, almost always associated with two molecular defects. In most EPP patients, clinical expression requires coinheritance of a private ferrochelatase (FECH) mutation trans- to a hypomorphic FECH*IVS3-48C allele. This leads to a decrease of FECH activity below the critical threshold. This is characterized by cutaneous photosensitivity in early childhood such as itching, burning, swelling and redness in sun-exposed areas. Hepatic failure occurs in some patients (about 1-10 % of EPP patients), which may necessitate liver transplantation. We investigated a Czech family with two patients with manifested EPP in four generations. We found a novel mutation, c.84G >A, in the FECH gene in four individuals including proband and his mother (G84A transition in exon 2; p.W28*). Both clinically manifested probands inherited the hypomorphic IVS3-48C allele as well, while two clinically latent individuals with FECH mutation did not. To address the question whether the relatively low incidence of EPP in the Czech Republic might be due to lower frequency of the IVS3-48C allele, we screened for the frequency of the low expression allele in a control Czech (West Slaves) Caucasian population. Such study has not been performed in any Slavic population. Among 312 control individuals, there were no IVS3-48C/C (c.68-23C-T) homozygotes; 35 IVS3-48C/T heterozygous individuals were detected. The frequency of IVS3-48C allele was thus found to be 5.5 % in the Czech population, comparable to most West Caucasian populations.

MeSH
Biosynthetic Pathways genetics MeSH
DNA genetics MeSH
Adult MeSH
Erythrocytes metabolism MeSH
Protoporphyria, Erythropoietic blood enzymology genetics MeSH
Ferrochelatase chemistry genetics MeSH
Genetic Predisposition to Disease * MeSH
Genome, Human MeSH
Heme biosynthesis MeSH
Humans MeSH
Adolescent MeSH
Molecular Sequence Data MeSH
Mutation genetics MeSH
DNA Mutational Analysis MeSH
Polymorphism, Genetic * MeSH
Protoporphyrins blood MeSH
Family MeSH
Pedigree MeSH
Amino Acid Sequence MeSH
Base Sequence MeSH
Check Tag
Adult MeSH
Humans MeSH
Adolescent MeSH
Male MeSH
Female MeSH
Publication type
Journal Article MeSH
Geographicals
Czech Republic MeSH

Online article

Functional assignments for the carboxyl-terminal domains of the ferrochelatase from Synechocystis PCC 6803: the CAB domain plays a regulatory role, and region II is essential for catalysis

Plant physiology. 2011 ; 155 (4) : 1735-47.

Plant Physiol
ISSN 1532-2548
Medvik
Source

Ferrochelatase (FeCH) catalyzes the insertion of Fe(2+) into protoporphyrin, forming protoheme. In photosynthetic organisms, FeCH and magnesium chelatase lie at a biosynthetic branch point where partitioning down the heme and chlorophyll (Chl) pathways occurs. Unlike their mammalian, yeast, and other bacterial counterparts, cyanobacterial and algal FeCHs as well as FeCH2 isoform from plants possess a carboxyl-terminal Chl a/b-binding (CAB) domain with a conserved Chl-binding motif. The CAB domain is connected to the FeCH catalytic core by a proline-rich linker sequence (region II). In order to dissect the regulatory, catalytic, and structural roles of the region II and CAB domains, we analyzed a FeCH ΔH347 mutant that retains region II but lacks the CAB domain and compared it with the ΔH324-FeCH mutant that lacks both these domains. We found that the CAB domain is not required for catalytic activity but is essential for dimerization of FeCH; its absence causes aberrant accumulation of Chl-protein complexes under high light accompanied by high levels of the Chl precursor chlorophyllide. Thus, the CAB domain appears to serve mainly a regulatory function, possibly in balancing Chl biosynthesis with the synthesis of cognate apoproteins. Region II is essential for the catalytic function of the plastid-type FeCH enzyme, although the low residual activity of the ΔH324-FeCH is more than sufficient to furnish the cellular demand for heme. We propose that the apparent surplus of FeCH activity in the wild type is critical for cell viability under high light due to a regulatory role of FeCH in the distribution of Chl into apoproteins.

MeSH
Acclimatization MeSH
Bacterial Proteins genetics metabolism MeSH
Chlorophyll biosynthesis MeSH
Ferrochelatase genetics metabolism MeSH
Protein Interaction Domains and Motifs MeSH
Protein Multimerization MeSH
Mutation MeSH
Light MeSH
Synechocystis enzymology genetics growth & development MeSH
Tetrapyrroles biosynthesis MeSH
Publication type
Journal Article MeSH
Research Support, Non-U.S. Gov't MeSH

Online article

The C-terminal extension of ferrochelatase is critical for enzyme activity and for functioning of the tetrapyrrole pathway in Synechocystis strain PCC 6803

Journal of bacteriology. 2008 ; 190 (6) : 2086-2095.

J Bacteriol
Medvik
Source

Heme and chlorophyll (Chl) share a common biosynthetic pathway up to the branch point where magnesium chelatase and ferrochelatase (FeCH) insert either magnesium for Chl biosynthesis or ferrous iron for heme biosynthesis. A distinctive feature of FeCHs in cyanobacteria is their C-terminal extension, which forms a putative transmembrane segment containing a Chl-binding motif. We analyzed the deltaH324 strain of Synechocystis sp. strain PCC 6803, which contains a truncated FeCH enzyme lacking this C-terminal domain. Truncated FeCH was localized to the membrane fraction, suggesting that the C-terminal domain is not necessary for membrane association of the enzyme. Measurements of enzyme activity and complementation experiments revealed that the deltaH324 mutation dramatically reduced activity of the FeCH, which resulted in highly upregulated 5-aminolevulinic acid synthesis in the deltaH324 mutant, implying a direct role for heme in the regulation of flux through the pathway. Moreover, the deltaH324 mutant accumulated a large amount of protoporphyrin IX, and levels of Chl precursors were also significantly increased, suggesting that some, but not all, of the "extra" flux can be diverted down the Chl branch. Analysis of the recombinant full-length and truncated FeCHs demonstrated that the C-terminal extension is critical for activity of the FeCH and that it is strictly required for oligomerization of this enzyme. The observed changes in tetrapyrrole trafficking and the role of the C terminus in the functioning of FeCH are discussed.

Online article

Effects of occupational exposure to diesel exhaust on porphyrin metabolism in lymphocytes of workers employed at black coal and oil-shale mines

American journal of industrial medicine. 2003 ; 44 (1) : 70-74. [pub] -

Am J Ind Med
ISSN 0271-3586
Medvik
Source

BACKGROUND: This pilot study was conducted to investigate biochemical effects of exposure to diesel engine exhaust at two mines. For this purpose, heme biosynthesis, and PP association with DNA (PP/DNA) in lymphocytes of miners exposed to diesel exhaust were determined. METHODS: The pilot study was carried out at a black coal mine in Czech Republic, and at an oil-shale mine in Estonia. The subjects were ten drivers from each mine, who were exposed to diesel exhaust (underground workers). Control groups consisted of ten maintenance workers from each mine (surface workers). The content of 1-nitropyrene (NP) in respirable dust was measured using GC-MS. The levels of PP, PP/DNA, heme, and activity of ferrochelatase (FC) were determined by spectrophotometry. RESULTS: The exposure to diesel exhaust evaluated as the level of NP associated to particulate matter in air. NP level was significantly higher in oil-shale mine compared with coal mine. The values of PP and PP/DNA in lymphocytes appeared to be significantly increased only in miners in the oil-shale mine. There was no difference in the levels of PP and PP/DNA and FC activity between surface workers and miners at the coal mine. The level of heme in lymphocytes of coal mine miners was significantly higher than in miners of the oil-shale mine. The activity of FC was significantly lower in underground workers compared to surface workers at this mine. High level of NP was accompanied by an increase of alterations in cells porphyrin metabolism in lymphocytes of miners. CONCLUSIONS: Alterations of porphyrin and heme metabolism in peripheral lymphocytes may serve as biomarker in assessment of exposure to diesel exhaust effects.