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Query: UMLS:C1832526 (PCC)
 5,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The regional distribution of N-methyl-D-aspartate (NMDA) receptors in rat brain using the selective NMDA receptor ligand [3H]3-[+/-)-2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) has been quantitated by in vitro autoradiography. [3H]CCP binding was highest in the CA1 region of the hippocampus. Relatively high levels of binding were also observed in the cerebral cortex, while moderate binding was obtained in the thalamus, striatum and granule cell layer of the cerebellum. Concurrent studies examining the phencyclidine receptor ligand [3H]1-[1-(2-thienyl)cyclohexyl]-piperidine (TCP), revealed a similar pattern of binding that correlated well with the localization of [3H]CPP-labeled NMDA receptors (r = 0.88, P less than 0.01).
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PMID:Quantitative autoradiographic localization of NMDA receptors in rat brain using [3H]CPP: comparison with [3H]TCP binding sites. 282 43

The degradation rate of the D1 polypeptide was measured in three Synechocystis PCC 6803 mutants in vivo. Mutations were introduced into a putative cleavage area of the D1 polypeptide (QEEET motif) and into the PEST-like area. PEST sequences are often found in proteins with a high turnover rate. The QEEET-motif mutants are CA1 [delta (E242-E244);Q241H] and E243K, and the third mutation, E229D, was directed to the PEST-like area. During high-light illumination (1500 mumol photons m-2 s-1) that induced photoinhibition of photosystem II (PSII), the half-life time of the D1 polypeptide in mutant E229D (t 1/2 = 35 min) was about twice as long as in AR (control strain) cells (t 1/2 = 19 min). In growth light (40 mumol photons m-2 s-1), the degradation rate of the D1 polypeptide in E229D and AR strains was the same (t 1/2 approximately 5 h). In growth light the D1 polypeptide was degraded faster in both QEEET-motif mutants than in the AR strain, but in photoinhibitory light the degradation rates were similar. According to these results, the highly conservative QEEET motif as such is not required for the proteolytic cut of the D1 polypeptide, but it does affect the rate of degradation. No simple correlation existed between the degradation rate of the D1 polypeptide and the susceptibility of PSII to photoinhibition in mutant and AR cells under our experimental conditions.
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PMID:Changes of amino acid sequence in PEST-like area and QEEET motif affect degradation rate of D1 polypeptide in photosystem II. 804 74

Ischemic neuronal injury appears to be mediated by disruption of subcellular ion distribution and, therefore, prevention of ion relocation might be neuroprotective. X-ray microanalysis was used to measure concentrations of Na, K, Ca and other elements in subcellular compartments (e.g., mitochondria) of CA1 neurons from oxygen/glucose-deprived (OGD) hippocampal slices. Results showed that OGD produced progressive loss of ion regulation in CA1 cells. Post-OGD reperfusion with normal media exacerbated the initial ion deregulation. To study neuroprotective mechanisms, we determined the ability of hypothermia (31 degrees C) or ion channel blockade to retard intraneuronal ion disruption induced by OGD/reperfusion. Whereas Ca2+ channel blockade (omega-conotoxin MVIIC, 3 microM) was ineffective, hypothermia and Na+ channel blockers (tetrodotoxin, TTX, 1 microM; lidocaine, 200 microM) reduced ion deregulation in subneuronal compartments. Blockade of glutamate receptors (AMPA, 10 microM; the non-NMDA receptor antagonist CNQX, 10 microM/100 microM glycine; the NMDA receptor antagonist CCP, 100 microM) during OGD/reperfusion provided nearly complete protection. These findings provide a foundation for identifying potential pharmacotherapeutic approaches and for discerning corresponding mechanisms of neuroprotection.
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PMID:Intraneuronal ion distribution during experimental oxygen/glucose deprivation. Routes of ion flux as targets of neuroprotective strategies. 1066 26

Photosystem II electron transfer, charge stabilization, and photoinhibition were studied in three site-specific mutants of the D1 polypeptide of Synechocystis PCC 6803: E243K, E229D, and CA1 (deletion of three glutamates 242-244 and a substitution, glutamine-241 to histidine). The phenotypes of the E229D and E243K mutants were similar to that of the control strain (AR) in all of the studied aspects. The characteristics of CA1 were very different. Formate, which inhibits the QA- to QB- reaction, was severalfold less effective in CA1 than in AR. The S2QA- and S2QB- states were stabilized in CA1. It was previously shown that the electron transfer between QA- and QB was modified in CA1 (P Maenpaa, T. Kallio, P. Mulo, G. Salih, E.-M. Aro, E. Tyystjarvi, C. Jansson [1993] Plant Mol Biol 22: 1-12). A change in the redox potential of the QA/QA- couple, which renders the reoxidation of QA- by back or forward reactions more difficult, could explain the phenotype of CA1. Although the rates of photoinhibition measured as inhibition of oxygen evolution, Chl fluorescence quenching, and decrease of thermoluminescence B and Q bands were similar in AR and CA1, the CA1 strain more quickly reached a state from which the cells were unable to recover their activity. The results described in this paper suggest that a modification in the structure of the D-de loop of D1 could influence the properties of the couple QA/QA- in D2 and the mechanism of recovery from photoinhibition.
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PMID:A Mutation in the D-de Loop of D1 Modifies the Stability of the S2QA- and S2QB- States in Photosystem II. 1222 53

Cyanophycin (multi-l-arginyl-poly-l-aspartic acid; also known as cyanophycin grana peptide [CGP]) is a putative precursor for numerous biodegradable technically used chemicals. Therefore, the biosynthesis and production of the polymer in recombinant organisms is of special interest. The synthesis of cyanophycin derivatives consisting of a wider range of constituents would broaden the applications of this polymer. We applied recombinant Saccharomyces cerevisiae strains defective in arginine metabolism and expressing the cyanophycin synthetase of Synechocystis sp. strain PCC 6308 in order to synthesize CGP with citrulline and ornithine as constituents. Strains defective in arginine degradation (Car1 and Car2) accumulated up to 4% (wt/wt) CGP, whereas strains defective in arginine synthesis (Arg1, Arg3, and Arg4) accumulated up to 15.3% (wt/wt) of CGP, which is more than twofold higher than the previously content reported in yeast and the highest content ever reported in eukaryotes. Characterization of the isolated polymers by different analytical methods indicated that CGP synthesized by strain Arg1 (with argininosuccinate synthetase deleted) consisted of up to 20 mol% of citrulline, whereas CGP from strain Arg3 (with ornithine carbamoyltransferase deleted) consisted of up to 8 mol% of ornithine, and CGP isolated from strain Arg4 (with argininosuccinate lyase deleted) consisted of up to 16 mol% lysine. Cultivation experiments indicated that the incorporation of citrulline or ornithine is enhanced by the addition of low amounts of arginine (2 mM) and also by the addition of ornithine or citrulline (10 to 40 mM), respectively, to the medium.
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PMID:Metabolic engineering of Saccharomyces cerevisiae for production of novel cyanophycins with an extended range of constituent amino acids. 1934 56

Light has been suggested to regulate both synthesis and degradation of the Photosystem II (PS II) reaction centre polypeptide D1, encoded by the psbA gene. The modified degradation rate of the D1 polypeptide in site-directed Synechocystis sp PCC 6803 D1 mutants CA1 [del(E242-E244);Q241H], E243K and E229D has provided a tool to determine whether the rate of D1 polypeptide synthesis is directly regulated by light-intensity-related factors or by a control mechanism mediated by light-dependent degradation of the D1 polypeptide. In vivo accumulation of [(35)S] methionine into the D1 polypeptide was found to correlate with D1 polypeptide degradation rather than with incident irradiance. This suggests that the degradation rate of the D1 polypeptide regulates its own synthesis at translational level. Furthermore, several fold differences in the psbA mRNA levels were measured between D1 mutant strains, indicating that the psbA gene transcription is not solely under light control.
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PMID:D1 polypeptide degradation may regulate psbA gene expression at transcriptional and translational levels in Synechocystis sp. PCC 6803. 2430 19