Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “PSAC”

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 19 recordsLinked to original sources
PubMed1991

PsaD is required for the stable binding of PsaC to the photosystem I core protein of Synechococcus sp. PCC 6301.

The psaC gene product from Synechococcus sp. PCC 7002 and the psaD gene product from Nostoc sp. PCC 8009 were synthesized in Escherichia coli and purified to homogeneity. Incubation of the PsaC apoprotein with the Synechoccus sp. PCC 6301 photosystem I core protein in the presence of FeCl3, Na2S, and beta-mercaptoethanol resulted in a time-dependent transition in the flash-induced absorption change from a 1.2-ms, P700+ FX- back-reaction to a long-lived, P700+ [FA/FB]- back-reaction. ESR studies showed that FB and FA were photoreduced about equally at 19 K, and while the resonances were shifted upfield, they remained as broad as in the free PsaC holoprotein. When the reconstituted complex was purified in a sucrose gradient containing 0.1% Triton X-100, most of the optical absorption transient reverted to that characteristic of the P700+ FX- back-reaction. Addition of purified PsaD to the incubation mixture led to a greater extent of recovery of electron flow to FA/FB for any given concentration of PsaC. ESR studies showed that FA, rather than FB, became the preferred electron acceptor at 19 K; moreover, the resonances moved upfield and sharpened to become nearly identical with those of a control photosystem I complex. When the sample was purified in a sucrose gradient containing 0.1% Triton X-100, the long-lived P700+ [FA/FB]- optical transient remained stable. Analysis by denaturing polyacrylamide gel electrophoresis showed that the PsaC and PsaD proteins had rebound to the photosystem I core. The data indicate that although PsaC can bind loosely, the presence of PsaD leads to a stable, isolatable photosystem I complex which is spectroscopically indistinguishable from the native complex. Since a PsaC1 fusion protein which contains an amino-terminal extension of five amino acids (MEHSM...) does not bind in the absence of PsaD [Zhao, J., et al. (1990) FEBS Lett. 276, 175-180], the N-terminus of the PsaC protein could provide a site of interaction with the photosystem I core. We propose that the binding of PsaC to the PsaA/PsaB heterodimer is potentiated by insertion of the FA/FB clusters into PsaC, and stabilized by the presence of PsaD.

Amino Acid Sequence↗
PubMed1991

Partial conservation of the 5' ndhE-psaC-ndhD 3' gene arrangement of chloroplasts in the cyanobacterium Synechocystis sp. PCC 6803: implications for NDH-D function in cyanobacteria and chloroplasts.

The psaC gene, which encodes the 8.9 kDa iron-sulfur containing subunit of Photosystem I, has been sequenced from Synechocystis sp. PCC 6803 and shows greater similarity to reported plant sequences than other cyanobacterial psaC sequences. The deduced amino acid sequence of the protein encoded by the Synechocystis psaC gene is identical to the tobacco PSA-C sequence. In plants psaC is located in the small single-copy region of the chloroplast genome between two genes (designated ndhE and ndhD) with similarity to genes encoding subunits of the mitochondrial NADH Dehydrogenase Complex I. The 5' ndhE-psaC-ndhD3' gene arrangement of higher plants is only partially conserved in Synechocystis. An open reading frame (ORF) upstream of the Synechocystis psaC gene has 85% identity to the tobacco ndhE gene. Downstream of psaC there is a 273 bp ORF with 48% identity to the 5' portion of the tobacco ndhD gene (1527 bp). psaC, ndhE and the region of similarity to ndhD are present in a single copy in the Synechocystis genome. Part of the wheat ndhD gene was sequenced and used as a probe for the presence of the 3' portion of the ndhD gene. The wheat ndhD probe did not hybridize to Synechocystis or Anabaena sp. PCC 7120 genomic DNA, but did hybridize to Oenothera chloroplast DNA. These results indicate the complete ndhD gene is absent in two cyanobacteria, and raises the question of what role, if any, the ndhD gene product plays in the facultative heterotroph Synechocystis sp. PCC 6803.

Amino Acid Sequence↗
PubMed1991

Directed chloroplast transformation in Chlamydomonas reinhardtii: insertional inactivation of the psaC gene encoding the iron sulfur protein destabilizes photosystem I.

The chloroplast gene psaC encoding the iron sulfur protein of photosystem I (PSI) from the green alga Chlamydomonas reinhardtii has been cloned and characterized. The deduced amino acid sequence is highly related to that of higher plants and cyanobacteria. Using a particle gun, wild type C. reinhardtii cells have been transformed with a plasmid carrying the psaC gene disrupted by an aadA gene cassette designed to express spectinomycin/streptomycin resistance in the chloroplast. Transformants selected on plates containing acetate as a reduced carbon source and spectinomycin are unable to grow on minimal medium lacking acetate and are deficient in PSI activity. Southern blot analysis of total cell DNA of the transformants shows that the wild type psaC gene has been replaced by the interrupted psaC gene through homologous recombination. While authentic transcripts of the psaC gene are no longer detected, aadA gives rise to a few transcripts in the transformants. Biochemical analysis indicates that neither PSI reaction center subunits nor the seven small subunits belonging to PSI accumulate stably in the thylakoid membranes of the transformants. Pulse-chase labeling of cell proteins shows that the PSI reaction center subunits are synthesized normally but turn over rapidly in the transformants. We conclude that the iron sulfur binding protein encoded by the psaC gene is an essential component, both for photochemical activity and for stable assembly of PSI. The present study suggests that any chloroplast gene encoding a component of the photosynthetic apparatus can be disrupted in C. reinhardtii using the strategy described.

Amino Acid Sequence↗
PubMed1992

The psaC genes of Synechococcus sp. PCC7002 and Cyanophora paradoxa: cloning and sequence analysis.

The psaC genes of the cyanobacterium, Synechococcus sp. PCC7002, and of the cyanelle genome of the phylogenetically ambiguous biflagellate, Cyanophora paradoxa, were cloned, mapped and sequenced. The PsaC proteins of both species exhibit high degrees (approx. 95%) of sequence similarity to the PsaC proteins of other cyanobacteria as well as the chloroplast-encoded proteins of green algae and higher plants. The Synechococcus sp. PCC7002 psaC gene is transcribed as a monocistronic mRNA of approx. 350-400 nt, and transcription is initiated 51 nt upstream from the translational start codon. As found for the chloroplasts of higher plants, the C. paradoxa psaC gene is encoded within the small single-copy region of the cyanelle genome. In contrast to results obtained for chloroplasts and for the cyanobacterium Synechocystis sp. PCC6803, neither psaC gene is flanked by genes encoding components of the NAD(P)H dehydrogenase complex.

Amino Acid Sequence↗
PubMed2025

The critical role of PSAC channel in malaria parasite survival is driven home by phenotypic screening under relevant nutrient levels.

Spreading resistance to front-line treatments necessitate the search for new classes of antimalarials. Limitations of standard screening conditions lead us to develop an assay using culture media that more closely reflects nutrient levels in human serum to reveal new therapeutically relevant parasite pathways. Our approach was validated by testing 22k compounds followed by a full 750k compound screen and identified 29 chemotypes with higher activity in nutrient restricted media that were further characterized. Through a combination of chemo-genomics and innovative photocatalytic proximity labeling proteomics, we identified the target of two compounds as the CLAG3 component of the plasmodial surface anion channel (PSAC). Strikingly, every one of the other 29 chemotypes selected was also found to block PSAC activity, highlighting the importance of this nutrient channel for parasite survival under physiological conditions. The effect of PSAC inhibitors in the in vivo humanized mouse model was confirmed.

Animals↗
PubMed1992

Identification of a second psaC gene in the cyanobacterium Synechocystis sp. PCC6803.

The psaC gene encodes the 9 kDa protein subunit of photosystem I that carries the iron-sulfur centers FA and FB. The paper describes the sequence and transcription analysis of a second psaC gene (psaC2) from Synechocystis sp. PCC6803. ThepsaC2 gene is transcribed into an abundant monocistronic mRNA. The deduced amino acid sequence of PSI-C2 is very similar to the protein sequences from two other cyanobacteria (Synechococcus sp. PCC7002 and Nostoc sp. PCC8009). In contrast, the recently isolated psaC1 gene is not transcribed and the PSI-C1 amino acid sequence shows the highest similarity to the proteins from higher plants.

Amino Acid Sequence↗
PubMed1992

Site-directed conversion of a cysteine to aspartate leads to the assembly of a [3Fe-4S] cluster in PsaC of photosystem I. The photoreduction of FA is independent of FB.

The terminal electron acceptors FA and FB exist as two [4Fe-4S] clusters located on the 8.9-kDa PsaC protein in photosystem I. We have used site-directed mutagenesis to produce a complementary pair of mutant PsaC proteins in which specific cysteine ligands to the [4Fe-4S] clusters were changed to aspartic acid residues. The mutant proteins, denoted C14D and C51D, were overproduced in Escherichia coli; the iron-sulfur clusters were inserted in vitro; and the reconstituted proteins were rebound to the P700-FX core of Synechococcus sp. PCC 6301 in the presence of the PsaD protein. In complexes reconstituted with C51D a rhombic ESR spectrum with g-values of 2.063, 1.934, and 1.879 in the reduced state identifies the intact [4Fe-4S] cluster as FB, while an intense axial spectrum with g-values of 2.020 and 1.997 in the oxidized state identifies the altered cluster in the aspartate site as a [3Fe-4S] cluster. The [3Fe-4S] cluster corresponding to FA can be reduced chemically with dithionite and photochemically by illumination at room temperature but is not reduced by illumination at 15 K. With reconstituted C14D a rhombic ESR spectrum with g-values of 2.043, 1.942, and 1.853 in the reduced state identified the unaltered [4Fe-4S] cluster as FA, while a complex spectrum with a gz-value of 2.194 and an asymmetric gx,y set of resonances between 2.092 and 1.999 indicates an altered cluster of unknown identity in the site containing the aspartate ligand. The ESR signals arising from the altered cluster corresponding to FB are not diminished by illumination at either room temperature or 15 K.(ABSTRACT TRUNCATED AT 250 WORDS)

Aspartic Acid↗
PubMed1990

Reconstitution of electron transport in photosystem I with PsaC and PsaD proteins expressed in Escherichia coli.

A fusion protein, denoted PsaC1, which contains an amino-terminal extension of five amino acids (MEHSM...) and is derived from an in vitro modified form of the psaC gene of Synechococcus sp. PCC 7002, has been over-expressed in Escherichia coli. The product of the psaD gene of Nostoc sp. PCC 8009 has similarly been over-expressed. The PsaC1 and PsaD proteins can be combined with the photosystem I core protein of Synechococcus sp. PCC 6301 to reconstitute electron transport from P700 to the terminal FA/FB acceptors. Reconstitution was found to be absolutely dependent on reinsertion of the iron-sulfur clusters in the PsaC1 apoprotein and on the presence of the PsaD protein. This implies that the PsaC1 holoprotein does not bind solely to the PsaA/PsaB heterodimer but rather that its interaction with these proteins is mediated through the PsaD protein.

Amino Acid Sequence↗
PubMed1991

Polypeptide composition of the Photosystem I complex and the Photosystem I core protein from Synechococcus sp. PCC 6301.

The polypeptide composition of the Photosystem I complex from Synechococcus sp. PCC 6301 was determined by sodium-dodecyl sulfate polyacrylamide gel electrophoresis and N-terminal amino acid sequencing. The PsaA, PsaB, PsaC, PsaD, PsaE, PsaF, PsaK and PsaL proteins, as well as three polypeptides with apparent masses less than 8 kDa and small amounts of the 12.6 kDa GlnB (PII) protein, wee present in the Photosystem I complex. No proteins homologous to the PsaG and PsaH subunits of eukaryotic Photosystem I complexes were detected. When the Photosystem I complex was treated with 6.8 M urea and ultrafiltered using a 100 kDa cutoff membrane, the resulting Photosystem I core protein was found to be depleted of the PsaC, PsaD and PsaE proteins. The filtrate contained the missing proteins, along with five proteolytically-cleaved polypeptides with apparent masses of less than 16 kDa and with N-termini identical to that of the PsaD protein. The PsaF and PsaL proteins, along with the three less than 8 kDa polypeptides, were not released from the Photosystem I complex to any significant extent, but low-abundance polypeptides with N-termini identical to those of PsaF and PsaL were found in the filtrate with apparent masses slightly smaller than those found in the native Photosystem I complex. When the filtrate was incubated with FeCl3, Na2S and beta-mercaptoethanol in the presence of the isolated Photosystem I core protein, the PsaC, PsaD and PsaE proteins were rebound to reconstitute a Photosystem I complex functional in light-induced electron flow from P700 to FA/FB. In the absence of the iron-sulfur reconstitution agents, there was little rebinding of the PsaC, psaD or PsaE proteins to the Photosystem I core protein. No binding of the truncated PsaD polypeptides occurred, either in the presence or absence of the iron-sulfur reagents. The reconstitution of the FA/FB iron-sulfur clusters thus appears to be a necessary precondition for rebinding of the PsaC, psaD and psaE proteins to the Photosystem I core protein.

Amino Acid Sequence↗
PubMedDate not supplied

[Environment, nutrition and intellectual development].

The differential effects of malnutrition and psychosocial cultural deprivation (PSAC) upon intellectual performance and psychomotor development were studied in 52 preschool children attending nursery schools in urban Santiago (Chile). Nutritional status was evaluated according to Gómez, intellectual performance according to Weschler's scale (WISP and WISC tests), psychomotor development according to the Denver Developmental Screening Test and PSAC according to a numerical scale constructed from maternal I.Q.; socioeconomic status (Graffar) and a psychological questionnaire the correlational analysis, undernutrition was assigned a single value calculated from the severity and duration of the disease. An inverse correlation of - 0.36 existed between malnutrition and intellectual performance, and of - 0.39 between malnutrition and psychomotor development. Also, there was an inverse and significant correlation of - 0.73 between PSAC and psychomotor development; there was no correlation between PSAC and intellectual performance. Verbal I.Q. was more affected (r = - 0.52) than manual I.Q. (r = - 0.18) and children malnourished during the first 6 months of life attained lower scores of I.Q. than normals. The duration of malnutrition (mild in all cases) had no influence upon subsequent I.Q. This study was the basis for a rehabilitation program (educational-nutritional) to be applied in preschool children from nonprivileged areas.

Affective Symptoms↗
PubMed1987

The gene for the 9 kd polypeptide, a possible apoprotein for the iron-sulfur centers A and B of the photosystem I complex, in tobacco chloroplast DNA.

The gene for the 9 kd polypeptide (a possible apoprotein for the iron-sulfur centers A and B) of photosystem I has been located in the small single-copy region of tobacco chloroplast DNA. This gene (psaC) was identified by comparing the N-terminal amino acid sequence of the spinach 9 kd polypeptide with the entire sequence of tobacco chloroplast genome. The gene organization is ndhE (101 codons)--263 bp spacer--psaC (81 codons)--94 bp spacer--ndhD (509 codons). Northern blot hybridization revealed that psaC is transcribed in the chloroplasts. The deduced amino acid sequence and secondary structure are presented. The predicted polypeptide is rich in cysteine residues and contains a unique repeated sequence.

Amino Acid Sequence↗
PubMed1989

[A new transluminal angioplasty for the treatment of arteriosclerosis obliterans].

A Peripheral Simpson Atherectomy Catheter (PSAC), which permits transluminal excision and removal of diseased intima, has been tested experimentally and clinically. The device consists of a tubular housing and a cutting mechanism to excise the intima protruding into the housing. Experimentally, vascular clay model was used to estimate its efficacy. Multiple passages improved lumen size and inner smoothness, and there was some difficulty to treat curved models. Clinically, 9 lesions in 7 patients of iliofemoral atheromatous disease were treated with PSAC. Recanalization was achieved successfully except for two lesions, one a soft atheroma and the other a curved vessel. No angiographic dissections or acute arterial occlusions occurred. Despite the procedure was complicated, it seemed safe and effective. In order to improve this method, an angioplastic catheter which had a laser probe in its housing was newly designed. Nd-YAG laser was irradiated with this catheter to the atherosclerotic lesions which were induced by a high cholesterol diet in rabbit. It left smoother surface and less thermal injury than usual irradiation with contact laser probe, but it needed more energy. These results showed that PSAC can be an alternative transluminal angioplasty and the new designed laser catheter is useful, but more experiments are required to establish these procedures.

Adult↗
PubMed1987

Identification of a chloroplast-encoded 9-kDa polypeptide as a 2[4Fe-4S] protein carrying centers A and B of photosystem I.

An improved procedure is reported for large-scale preparation of photosystem I (PS-I) vesicles from thylakoid membranes of barley (Hordeum vulgare L.). The PS-I vesicles contain polypeptides of molecular masses 82, 18, 16, 14, and 9 kDa in an apparent molar ratio of 4:2:2:1:2. The 18-, 16-, and 9-kDa polypeptides were purified to homogeneity after exposure of the PS-I vesicles to chaotropic agents. The isolated 9-kDa polypeptide binds 65-70% of the zero-valence sulfur of denatured PS-I vesicles, and the remaining 30-35% is bound to P700-chlorophyll a-protein 1. The N-terminal amino acid sequence (29 residues) of the 9-kDa polypeptide was determined. Comparison with the nucleotide sequence of the chloroplast genome of Marchantia polymorpha (Ohyama, K., Fukuzawa, H., Kohchi, T., Shirai, H., Sano, T., Sano, S., Umesono, K., Shiki, Y., Takeuchi, M., Chang, Z., Aota, S.-i., Inokuchi, H., and Ozeki, H. (1986) Nature 322, 572-574) and of Nicotiana tabacum (Shinozaki, K., Ohme, M., Tanaka, M., Wakasugi, T., Hayashida, N., Matsubayashi, T., Zaita, W., Chunwongse, J., Obokata, J., Yamaguchi-Shinozaki, K., Ohto, C., Torazawa, K., Meng, B. Y., Sugita, M., Deno, H., Kamogashira, T., Yamada, K., Kusuda, J., Takaiwa, F., Kato, A., Tohdoh, N., Shimada, H., and Sugiura, M. (1986) EMBO J. 5, 2043-2049) identified the chloroplast gene encoding the 9-kDa polypeptide. We designate this gene psaC. The complete amino acid sequence deduced from the psaC gene identifies the 9-kDa PS-I polypeptide as a 2[4Fe-4S] protein. Since P700-chlorophyll a-protein 1 carries center X, the 9-kDa polypeptide carries centers A and B. A hydropathy plot permits specific identification of the cysteine residues which coordinate centers A and B, respectively. Except for the loss of the N-terminal methionine residue, the primary translation product of the psaC gene is not proteolytically processed. P700-chlorophyll a-protein 1 binds 4 iron atoms and 4 molecules of acid-labile sulfide/molecule of P700. Each of the two apoproteins of P700-chlorophyll a-protein 1 contains the sequence Phe-Pro-Cys-Asp-Gly-Pro-Gly-Arg-Gly-Gly-Thr-Cys (Fish, L. E., Kück, U., and Bogorad, L. (1985) J. Biol. Chem. 260, 1413-1421). The stoichiometry of the component polypeptides of PS-I indicates the presence of four copies of this sequence per molecule of P700. Center X may be composed of two [2Fe-2S] centers bound to the 8 cysteine residues contained in these four segments.

Amino Acid Sequence↗
PubMed1992

Nucleotide sequence and expression of the gene for the 9 kDa FA/FB component of photosystem I from the cyanobacterium Anabaena sp. PCC7120.

The nucleotide sequence of an 813 bp Ssp I-Hinc II fragment containing the psaC gene from Anabaena sp. PCC 7120 is reported. The gene encodes a polypeptide of 81 amino acids, has a single transcript of size approximately 480 nucleotides and a single startpoint of transcription. It is flanked by a ribosome binding site on the 5' end and a potential transcription terminator on the 3' end. Comparison of the amino acid sequences of the psaC gene product from sixteen organisms shows that cyanobacteria group as a cluster distinct from monocotyledonous and dicotyledonous plants and that individual amino acids are diagnostic of each cluster.

Amino Acid Sequence↗
PubMed1992

Cloning and transcription analysis of the ndh(A-I-G-E) gene cluster and the ndhD gene of the cyanobacterium Synechocystis sp. PCC6803.

The plastid DNA of higher plants contains eleven reading frames that are homologous to subunits of the mitochondrial NADH-ubiquinone oxidoreductase (complex I). The genes are expressed, but a plastid NAD(P)H dehydrogenase has not yet been isolated and the function of the enzyme in plastid metabolism is unknown. Cyanobacteria also contain a NADH dehydrogenase that is homologous to the mitochondrial complex I. The enzyme is sensitive to rotenone and is located on the cytoplasmic and the thylakoid membrane. We report here the sequence of five subunits (ndhA, -I, G, -E and -D) of the NADH dehydrogenase from the unicellular cyanobacterium Synechocystis sp. PCC6803. As in plastid DNA, the genes ndh(A-I-G-E) are clustered and probably constitute an operon. The ndhD gene is associated with a gene encoding an iron-sulphur protein of photosystem I (psaC) as in plastid DNA. In contrast to the situation in plastids, psaC and ndhD are not cotranscribed but transcribed from opposite strands. The deduced amino acid sequence of the cyanobacterial polypeptides is more similar to the corresponding plastid (40-68% identity) than to the corresponding mitochondrial subunits (17-39% identity). Thus, the cyanobacterial NADH-dehydrogenase provides a prokaryotic model system which is more suitable to genetic analysis than the enzyme of plastids.

Amino Acid Sequence↗
PubMed1989

Nucleotide sequences of cDNA clones encoding the entire precursor polypeptide for subunit VI and of the plastome-encoded gene for subunit VII of the photosystem I reaction center from spinach.

Recombinant phage which encode the entire precursor polypeptide for subunit VI of the photosystem I reaction center have been selected from a lambda gt11 cDNA expression library made from polyadenylated RNA of spinach seedlings. The sequence predicts a precursor polypeptide of 144 amino acids (Mr = 15.3 kDa), a mature protein of 95 residues (Mr = 10.4 kDa) that lacks methionine, histidine and cysteine, and a transit peptide of 49 residues (Mr = 4.9 kDa). The corresponding gene(s) is (are) designated psaH. The gene for subunit VII, psaC, has been located in the small single-copy region of the spinach plastid chromosome using a synthetic oligonucleotide and a heterologous hybridization probe. It is part of a polycistronic transcription unit that is constitutively expressed and processed. Putative processing products include a monocistronic RNA for psaC. The polypeptide chain of 18 (deduced) amino acids is highly conserved and strikingly resembles bacterial-type ferredoxins. It harbours cysteine residues that appear to be involved in the ligation of the two 4Fe4S centres A and B in photosystem I. None of the two subunits appears to be membrane-spanning, and subunit VI, as subunit VII, is located at the reducing (stromal) side of the reaction center. All available information on the major subunits of photosystem I from spinach has been combined into a (revised) topographic model. Evidence that the innermost - plastome-encoded - core of photosystem I represents an old bacterial heritage in present day chloroplasts is discussed.

Amino Acid Sequence↗