Biomedical subjects

H C Matthijs

Publications and source records attributed to H C Matthijs.

13 recordsLinked to original sources

PubMed2000

Salt shock-inducible photosystem I cyclic electron transfer in Synechocystis PCC6803 relies on binding of ferredoxin:NADP(+) reductase to the thylakoid membranes via its CpcD phycobilisome-linker homologous N-terminal domain.

Relative to ferredoxin:NADP(+) reductase (FNR) from chloroplasts, the comparable enzyme in cyanobacteria contains an additional 9 kDa domain at its amino-terminus. The domain is homologous to the phycocyanin associated linker polypeptide CpcD of the light harvesting phycobilisome antennae. The phenotypic consequences of the genetic removal of this domain from the petH gene, which encodes FNR, have been studied in Synechocystis PCC 6803. The in frame deletion of 75 residues at the amino-terminus, rendered chloroplast length FNR enzyme with normal functionality in linear photosynthetic electron transfer. Salt shock correlated with increased abundance of petH mRNA in the wild-type and mutant alike. The truncation stopped salt stress-inducible increase of Photosystem I-dependent cyclic electron flow. Both photoacoustic determination of the storage of energy from Photosystem I specific far-red light, and the re-reduction kinetics of P700(+), suggest lack of function of the truncated FNR in the plastoquinone-cytochrome b(6)f complex reductase step of the PS I-dependent cyclic electron transfer chain. Independent gold-immunodecoration studies and analysis of FNR distribution through activity staining after native polyacrylamide gelelectrophoresis showed that association of FNR with the thylakoid membranes of Synechocystis PCC 6803 requires the presence of the extended amino-terminal domain of the enzyme. The truncated DeltapetH gene was also transformed into a NAD(P)H dehydrogenase (NDH1) deficient mutant of Synechocystis PCC 6803 (strain M55) (T. Ogawa, Proc. Natl. Acad. Sci. USA 88 (1991) 4275-4279). Phenotypic characterisation of the double mutant supported our conclusion that both the NAD(P)H dehydrogenase complex and FNR contribute independently to the quinone cytochrome b(6)f reductase step in PS I-dependent cyclic electron transfer. The distribution, binding properties and function of FNR in the model cyanobacterium Synechocystis PCC 6803 will be discussed.

Amino Acid Sequence↗

PubMed1999

Kinetic evidence for the PsaE-dependent transient ternary complex photosystem I/Ferredoxin/Ferredoxin:NADP(+) reductase in a cyanobacterium.

A mutant of Synechocystis PCC 6803, deficient in psaE, assembles photosystem I reaction centers without the PsaE subunit. Under conditions of acceptor-side rate-limited photoreduction assays in vitro (with 15 microM plastocyanin included), using 100 nM ferredoxin:NADP(+) reductase (FNR) and either Synechocystis flavodoxin or spinach ferredoxin, lower rates of NADP(+) photoreduction were measured when PsaE-deficient membranes were used, as compared to the wild type. This effect of the psaE mutation proved to be due to a decrease of the apparent affinity of the photoreduction assay system for the reductase. In the psaE mutant, the relative petH (encoding FNR) expression level was found to be significantly increased, providing a possible explanation for the lack of a phenotype (i.e., a decrease in growth rate) that was expected from the lower rate of linear electron transport in the mutant. A kinetic model was constructed in order to simulate the electron transfer from reduced plastocyanin to NADP(+), and test for possible causes for the observed change in affinity for FNR. The numerical simulations predict that the altered reduction kinetics of ferredoxin, determined for the psaE mutant [Barth, P., et al., (1998) Biochemistry 37, 16233-16241], do not significantly influence the rate of linear electron transport to NADP(+). Rather, a change in the dissociation constant of ferredoxin for FNR does affect the saturation profile for FNR. We therefore propose that the PsaE-dependent transient ternary complex PSI/ferredoxin/FNR is formed during linear electron transport. Using the yeast two-hybrid system, however, no direct interaction could be demonstrated in vivo between FNR and PsaE fusion proteins.

Base Sequence↗

PubMed1999

Localization and function of ferredoxin:NADP(+) reductase bound to the phycobilisomes of Synechocystis.

Each phycobilisome complex of the cyanobacterium Synechocystis PCC 6803 binds approximately 2.4 copies of ferredoxin:NADP(+) reductase (FNR). A mutant of this strain that carries an N-terminally truncated version of the petH gene, lacking the 9 kDa domain of FNR that is homologous to the phycocyanin-associated linker polypeptide CpcD, assembles phycobilisome complexes that do not contain FNR. Phycobilisome complexes, consisting of the allophycocyanin core and only the core-proximal phycocyanin hexamers from mutant R20, do contain a full complement of FNR. Therefore, the binding site of FNR in the phycobilisomes is not the core-distal binding site that is occupied by CpcD, but in the core-proximal phycocyanin hexamer. Phycobilisome complexes of a mutant expressing a fusion protein of the N-terminal domain of FNR and green fluorescent protein (GFP) contain this fusion protein in tightly bound form. Calculations of the fluorescence resonance energy transfer (FRET) characteristics between GFP and acceptors in the phycobilisome complex indicate that their donor-acceptor distance is between 3 and 7 nm. Fluorescence spectroscopy at 77K and measurements in intact cells of accumulated levels of P700(+) indicate that the presence of FNR in the phycobilisome complexes does not influence the distribution of excitation energy of phycobilisome-absorbed light between photosystem II and photosystem I, and also does not affect the occurrence of 'light-state transitions'.

Bacterial Proteins↗

PubMed1999

Chlorophyll b and phycobilins in the common ancestor of cyanobacteria and chloroplasts.

Photosynthetic organisms have a variety of accessory pigments, on which their classification has been based. Despite this variation, it is generally accepted that all chloroplasts are derived from a single cyanobacterial ancestor. How the pigment diversity has arisen is the key to revealing their evolutionary history. Prochlorophytes are prokaryotes which perform oxygenic photosynthesis using chlorophyll b, like land plants and green algae (Chlorophyta), and were proposed to be the ancestors of chlorophyte chloroplasts. However, three known prochlorophytes (Prochloron didemni, Prochlorothrix hollandica and Prochlorococcus marinus) have been shown to be not the specific ancestors of chloroplasts, but only diverged members of the cyanobacteria, which contain phycobilins but lack chlorophyll b. Consequently it has been proposed that the ability to synthesize chlorophyll b developed independently several times in prochlorophytes and in the ancestor of chlorophytes. Here we have isolated the chlorophyll b synthesis genes (chlorophyll a oxygenase) from two prochlorophytes and from major groups of chlorophytes. Phylogenetic analyses show that these genes share a common evolutionary origin. This indicates that the progenitors of oxygenic photosynthetic bacteria, including the ancestor of chloroplasts, had both chlorophyll b and phycobilins.

Amino Acid Sequence↗

PubMed1998

Characterization and transcriptional regulation of the Synechocystis PCC 6803 petH gene, encoding ferredoxin-NADP+ oxidoreductase: involvement of a novel type of divergent operator.

The petH gene, encoding ferredoxin-NADP+ oxidoreductase (FNR), has been characterised in the unicellular cyanobacterium Synechocystis PCC 6803. Its product, FNR, was heterologously produced and functionally characterized. The start-site of the monocystronic petH transcript was mapped 523 bp upstream of the predicted PetH initiation codon, resulting in an unusually large 5'-untranslated region. The 5' end of the petH transcript is situated within the open reading frame of phosphoribulokinase (encoded by prk), which is transcribed in opposite orientation with respect to petH. The transcription start site of the prk transcript was mapped 219 bp upstream of the initiation codon, resulting in a 223 bp antisense region between both transcripts. Under many conditions the expression of both genes (i.e. petH and prk) is co-regulated symmetrically at the transcriptional level, as was concluded from both northern hybridization experiments and from primer extension analyses; it became uncoupled, however, when specifically petH expression was stimulated, independent of prk expression, by stressing the Synechocystis cells with high salt concentrations. A model for a new type of bidirectional operator, regulating the expression of petH and prk, is proposed.

Bacterial Proteins↗

PubMed1994

Expression of Anabaena PCC 7937 plastocyanin in Synechococcus PCC 7942 enhances photosynthetic electron transfer and alters the electron distribution between photosystem I and cytochrome-c oxidase.

The petE gene encoding plastocyanin precursor protein from the cyanobacterium Anabaena PCC 7937 was introduced in the cyanobacterial host strain Synechococcus PCC 7942. The host normally only uses cytochrome c553 as Photosystem I (PS I) donor. The heterologous gene was efficiently expressed using the inducible Escherichia coli trc promoter. Accumulation of plastocyanin protein depended on the presence of Cu2+. The protein was accurately targeted to the thylakoid lumen, from which it could be isolated in the mature form. Redox difference spectroscopy proved the presence of a Cu2+ ion in the holoenzyme. Isolated heterologous plastocyanin was functional in reconstitution of in vitro electron transfer to PS I. The presence of Anabaena plastocyanin in Synechococcus thylakoid membranes increased PS I electron transfer rate 2.5 times. Analysis of P700 redox and PS II fluorescence transients in vivo showed a faster electron transfer through PS I because of enhanced electron supply in the presence of plastocyanin. In addition, the distribution of electrons between photosynthetic and respiratory electron transfer changed. Plastocyanin preferentially donates electrons to PS I rather than to the respiratory cytochrome-c oxidase complex and is not functionally equivalent to cytochrome c553.

Anabaena↗

PubMed1994

In vivo manipulation of the xanthophyll cycle and the role of zeaxanthin in the protection against photodamage in the green alga Chlorella pyrenoidosa.

Chlorella pyrenoidosa was grown in steady-state continuous cultures in either high or low light. Samples of these cultures were incubated in darkness (violaxanthin state) or in saturating light (zeaxanthin state). These samples were kept in the respective preadapted states throughout the entire photodamage treatment. Photodamage involved exposure to single-turnover flashes fired at a low (non-actinic) frequency. The damage caused by the light stress thus applied was monitored by changes in photosynthetic properties and pigment composition. Cells preadapted in the light resisted photodamage better than those kept in darkness. The low light grown cells were more vulnerable to photodamage than the high light grown cells. Our experimental approach permitted the equilibria between the components that participate in the xanthophyll cycle to be set without addition of inhibitors. Regardless of the total amount of violaxanthin being present, its conversion to anthera- and zeaxanthin is a prerequisite for protection. The protection is most effective for photosystem II. It appeared that antheraxanthin accumulates as a result of photodamaging flashes provided that these are fired in the presence of background light, i.e. with zeaxanthin present. From this, it is newly derived that the xanthophyll cycle operates in full in the light, including epoxidation of zeaxanthin. The latter conversion was also demonstrated in vitro, via nonenzymatic oxygen-dependent turnover of zeaxanthin into violaxanthin.

Carotenoids↗

PubMed1994

Photobiology of bacteria.

The field of photobiology is concerned with the interactions between light and living matter. For Bacteria this interaction serves three recognisable physiological functions: provision of energy, protection against excess radiation and signalling (for motility and gene expression). The chemical structure of the primary light-absorbing components in biology (the chromophores of photoactive proteins) is surprisingly simple: tetrapyrroles, polyenes and derivatised aromats are the most abundant ones. The same is true for the photochemistry that is catalysed by these chromophores: this is limited to light-induced exciton- or electron-transfer and photoisomerization. The apoproteins surrounding the chromophores provide them with the required specificity to function in various aspects of photosynthesis, photorepair, photoprotection and photosignalling. Particularly in photosynthesis several of these processes have been resolved in great detail, for others at best only a physiological description can be given. In this contribution we discuss selected examples from various parts of the field of photobiology of Bacteria. Most examples have been taken from the purple bacteria and the cyanobacteria, with special emphasis on recently characterised signalling photoreceptors in Ectothiorhodospira halophila and in Fremyella diplosiphon.

Bacteria↗

PubMed1988

Supramolecular structure of the thylakoid membrane of Prochlorothrix hollandica: a chlorophyll b-containing prokaryote.

Prochlorothrix hollandica is a newly described photosynthetic prokaryote, which contains chlorophylls a and b. In this paper we report the results of freeze fracture and freeze etch studies of the organization of the photosynthetic thylakoid membranes of Prochlorothrix. These membranes exhibit four distinct fracture faces in freeze fractured preparations, two of which are derived from membrane splitting in stacked regions of the thylakoid membrane, and two of which are derived from nonstacked regions. The existence of these four faces confirms that the thylakoid membranes of Prochlorothrix, like those of green plants, display true membrane stacking and have different internal composition in stacked and non-stacked regions, a phenomenon that has been given the name lateral heterogeneity. The general details of these fracture faces are similar to those of green plants, although the intramembrane particles of Prochlorothrix are generally smaller than those of green plants by as much as 30%. Freeze etched membrane surfaces have also been studied, and the results of these studies confirm freeze fracture observations. The outer surface of the thylakoid membrane displays both small (less than 8.0 nm) and large (greater than 10.0 nm) particles. The inner surface of the thylakoid membrane is covered with tetrameric particles, which are concentrated into stacked membrane regions, a situation that is similar to the inner surfaces of the thylakoid membranes of green plants. These tetramers have never before been reported in a prokaryote. The photosynthetic membranes of Prochlorothrix therefore represent a prokaryotic system that is remarkably similar, in structural terms, to the photosynthetic membranes found in chloroplasts of green plants.

Chloroplasts↗

PubMed1987

Chlorophyll-protein composition of the thylakoid membrane from Prochlorothrix hollandica, a prokaryote containing chlorophyll b.

The chlorophyll-protein complexes of the thylakoid membrane from Prochlorothrix hollandica were identified following electrophoresis under nondenaturing conditions. Five complexes, CP1-CP5, were resolved and these green bands were analyzed by spectroscopic and immunological methods. CP1 contains the photosystem I (PSI) reaction center, as this complex quenched fluorescence at room temperature, and had a 77 K fluorescence emission peak at 717 nm. CP4 contains the major chlorophyll-a-binding proteins of the photosystem II (PSII) core, because this complex contained polypeptides which cross-reacted to antibodies raised against Chlamydomonas PSII proteins 5 and 6. Furthermore, fluorescence excitation studies at 77 K indicated that only a Chl a is bound to CP4. Complexes CP2, CP3 and CP5 contained functionally bound Chl a and b as judged by absorption spectroscopy at 20 degrees C and fluorescence excitation spectra at 77 K. CP2, CP3 and CP5 all contain polypeptides of 30-33 kDa which are immunologically distinct from the LHC-II complex of higher plant thylakoids.

Chlorophyll↗

PubMed1986

Removal of ferredoxin:NADP+ oxidoreductase from thylakoid membranes, rebinding to depleted membranes, and identification of the binding site.

Ferredoxin-NADP+ oxidoreductase associates with thylakoid membranes into two pools of different binding strength that are experimentally distinguished on the basis of resistance to removal by washes in low ionic strength media. The nondenaturing zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid is uniquely able to remove the more tightly bound pool of enzyme, without solubilization of major membrane proteins. The reconstitution of reductase onto depleted thylakoid membranes requires available membrane binding sites and cations, in order of effectiveness trivalent greater than divalent greater than monovalent. The hetero/bifunctional 125I-iodinated Denny-Jaffe cross-linking reagent yields a 54-kDa, covalently cross-linked adduct between ferredoxin-NADP+ oxidoreductase and a component of the thylakoid membrane. Our results show that the more tightly bound pool of enzyme is associated with the 17.5-kDa reductase-binding protein (Vallejos, R. H., Ceccarelli, E., and Chan, R. (1984) J. Biol. Chem. 259, 8048-8051).

Binding Sites↗

PubMed1985

The ferredoxin-NADP+ oxidoreductase-binding protein is not the 17-kDa component of the cytochrome b/f complex.

The complex between ferredoxin-NADP+ oxidoreductase and its proposed membrane-binding protein (Vallejos, R. H., Ceccarelli, E., and Chan, R. (1984) J. Biol. Chem. 259, 8048-8051) was isolated from spinach thylakoids and compared with isolated cytochrome b/f complex containing associated ferredoxin NADP+ oxidoreductase (Clark, R. D., and Hind, G. (1983) J. Biol. Chem. 258, 10348-10354). There was no immunological cross-reactivity between the 17.5-kDa binding protein and an antiserum raised against the 17-kDa polypeptide of the cytochrome complex. Association of ferredoxin-NADP+ oxidoreductase with the binding protein or with the thylakoid membrane gave an allotopic shift in the pH profile of diaphorase activity, as compared to the free enzyme. This effect was not seen in enzyme associated with the cytochrome b/f complex. Identification of the 17.5-kDa binding protein as the 17-kDa component of the cytochrome b/f complex is ruled out by these results.

Binding Sites↗

PubMedDate not supplied

Rhodopsin(s) in eubacteria.

While the biochemical basis of photosynthesis by bacteriochlorophyll-based reaction centres in purple phototrophic Eubacteria and retinal-based bacteriorhodopsin in the Archaebacterium Halobacterium salinarium has been elucidated in great detail, much less is known about photosensory signal transduction; this is especially the case for Eubacteria. Recent findings on two different photosensory proteins in two different Eubacteria, which both show clear resemblances to the rhodopsins, will be presented. The photoactive yellow protein (PYP) from the purple phototrophic organism Ectothiorhodospira halophila probably functions as the photoreceptor for a new type of negative phototaxis response and has been studied in some detail with respect to its structural and photochemical characteristics. On basis of crystallographic an photochemical data it has been proposed that PYP contains retinal as a chromophore. However, we have unambiguously demonstrated that the PYP chromophore is different from retinal, in spite of the fact that PYP's photochemical properties show striking similarities with the rhodopsins. The cyanobacterium Calothrix sp. displays complementary chromatic adaptation, a process in which the pigment composition of the phycobilisomes is adjusted to the spectral characteristics of the incident light. In orange light the blueish chromophore phycocyanin is present, in green light the reddish phycoerythrin is synthesized. On the basis of the action spectrum of this adaptation process, we hypothesized that a rhodopsin is the photosensor in this process. In line with this, we found that nicotine, an inhibitor of the biosynthesis of beta-carotene (which is the precursor of retinal), abolishes chromatic adaptation. Direct proof of the involvement of a photosensory rhodopsin was obtained in experiments in which the chromatic adaptation response was restored by the addition of retinal to the cultures. The two photosensory proteins mentioned above represent the first examples of eubacterial photoreceptors that can be studied at a molecular level. Our current knowledge on these two proteins and their status as retinal proteins will be reviewed.

Journal Article↗