Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C1832526 (PCC)
 5,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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)
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PMID: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. 131 44

Ascorbate peroxidase active component (APAC) was purified and characterized in Synechococcus PCC 9742 (R2) cells. APAC was isolated from freshly harvested cells, by ion exchange chromatography on DEAE cellulose, ultrafiltration through a 3000 dalton cut off filter and high pressure liquid chromatography through a reversed phase C-18 column. APAC was found to be extremely stable to harsh treatments of boiling water for 30 min, acidification to pH 2.0 and proteolytic digestion. A close correlation between activity and iron content of APAC was observed throughout the purification steps. E.S.R. spectrum of APAC showed a resonance line at g = 4.3 in the oxidized from. Peroxide reduction by ascorbate decreased the E.S.R. signal, which reappeared upon reoxidation by H2O2. The affinities of APAC to H2O2 and ascorbate were high (0.38 mM and 0.2 mM, respectively). Amino acid composition analysis of APAC revealed the presence of glutamic acid:glycine:cysteine residues at 2:1:1 ratio.
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PMID:A unique ascorbate peroxidase active component in the cyanobacterium Synechococcus PCC 7942 (R2). 133 15

Arginine auxotrophs of the dinitrogen-fixing cyanobacterium Anabaena species strain PCC 7120 were isolated after ultraviolet light mutagenesis and penicillin enrichment. Two of these auxotrophs were complemented by a cosmid gene library of the wild-type strain established in Escherichia coli that was transferred en masse to the mutants by conjugation. The gene complementing one of those mutants was found to complement an E. coli argC mutant. Sequencing analysis of the gene showed that it encodes a 322-residue polypeptide that is homologous to the ArgC protein of E. coli, Bacillus subtilis and Streptomyces clavuligerus and to the C-terminal moiety of the Saccharomyces cerevisiae ARG5,6 gene product, N-acetylglutamate semialdehyde dehydrogenase. A cysteine residue present in a highly conserved domain in the five proteins is probably located in the active site of the enzyme. Conserved among the ArgC proteins, sequences resembling the primary structure of nucleotide-binding domains are also found. Downstream of the Anabaena argC gene seven nearly perfect repeats of a heptanucleotide (consensus sequence:5'-CTAATGA-3') are found.
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PMID:Isolation of arginine auxotrophs, cloning by mutant complementation, and sequence analysis of the argC gene from the cyanobacterium Anabaena species PCC 7120. 140 50

The structural gene encoding a thioredoxin-dependent 5'-phosphoadenylyl sulphate (PAPS) reductase (EC 1.8.4.-) from cyanobacterium Synechococcus PCC 7942 ('Anacystis nidulans') was detected by heterologous hybridization with the cysH gene from Escherichia coli K12. The cyanobacterial gene (further called par gene) comprised 696 nt which are 57.8% homologous to the enterobacterial gene. The putative open reading frame encoded a polypeptide consisting of 232 amino acid residues (deduced molecular weight 26,635) which showed significant homologies to the polypeptide from E. coli (50.8%) and to the polypeptide from Saccharomyces cerevisiae (30.3%). A single cysteine located at the C-terminus of the polypeptide of E. coli (Cys239) was conserved in Synechococcus. Conservation of this cysteinyl residue seems indispensable for catalysis. Complementation of a cysH-deficient mutant of E. coli by the cyanobacterial gene indicated that the cloned DNA is the structural gene of the PAPS reductase.
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PMID:Primary structure of the Synechococcus PCC 7942 PAPS reductase gene. 146 52

Phycobiliproteins, unlike other light-harvesting proteins involved in photosynthesis, bear covalently attached chromophores. The bilin chromophores are attached through thioether bonds to cysteine residues. The cyanobacterium Synechococcus sp. PCC 7002 has eight distinct bilin attachment sites on seven polypeptides, all of which carry the same chromophore, phycocyanobilin. When two genes in the phycocyanin operon of this organism, cpcE and cpcF, are inactivated by insertion, together or separately, the surprising result is elimination of correct bilin attachment at only one site, that on the alpha subunit of phycocyanin. We have overproduced CpcE and CpcF in Escherichia coli. In vitro, these proteins catalyze the attachment of phycocyanobilin to the alpha subunit of apophycocyanin at the appropriate site, alpha-Cys-84, to form the correct adduct. CpcE and CpcF also efficiently catalyze the reverse reaction, in which the bilin from holo-alpha subunit is transferred either to the apo-alpha subunit of the same C-phycocyanin or to the apo-alpha subunit of a heterologous C-phycocyanin. The forward and reverse reactions each require both CpcE and CpcF and are specific for the alpha-Cys-84 position. Phycocyanobilin is the immediate precursor of the protein-bound bilin.
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PMID:Phycocyanin alpha-subunit phycocyanobilin lyase. 149 95

O6-Alkylguanine-DNA-alkyltransferase (O6-AGT) is a very important DNA repair protein known to carry out the transfer of alkyl groups from the O6 position of guanine in alkylated DNA to a cysteine acceptor site contained within its own protein sequence. In this work, the activity of O6-AGT in different cell lines and the relationship between the depletion of the enzyme and the frequency of micronuclei induced by cisplatin (DDP), Ning Xin platin (camphoramine chloroacetic platinum, CCP) or carboplatin (JM-8) in KB and CHL cells were studied. Experiments indicate that KB cells showed higher O6-AGT activity (greater than 400 dpm/300 micrograms protein extracts) which belonged to Mer+ cells, but CHL, HL-60 and L1210 cells showed very low O6-AGT activity (less than 50 dpm/300 micrograms protein extracts) which can be considered to be Mer- cells. Cytotoxicity studies indicated that no mer- selection was observed in these platinum complexes for KB, HL-60, CHL and L1210 cells. However, a good relationship between the depletion of O6-AGT and the frequency of micronuclei induced by the platinum complexes was obtained. CCP caused the highest depletion of the enzyme and exhibited highest potency in damaging chromosome.
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PMID:[Depletion of O6-alkylguanine alkyltransferase and chromosome damage induced by cisplatin, ning xin platin and carboplatin]. 180 17

The molecular structure of the oxidized form of the [2Fe-2S] ferredoxin isolated from the cyanobacterium Anabaena species strain PCC 7120 has been determined by X-ray diffraction analysis to a nominal resolution of 2.5 A and refined to a crystallographic R factor of 18.7%. Crystals used in this investigation belong to the space group P2(1)2(1)2(1) with unit cell dimensions of a = 37.42 A, b = 38.12 A, and c = 147.12 A and two molecules in the asymmetric unit. The three-dimensional structure of this ferredoxin was solved by a method that combined X-ray data from one isomorphous heavy-atom derivative with noncrystallographic symmetry averaging and solvent flattening. As in other plant-type [2Fe-2S] ferredoxins, the iron-sulfur cluster is located toward the outer edge of the molecule, and the irons are tetrahedrally coordinated by both inorganic sulfurs and sulfurs provided by protein cysteine residues. The main secondary structural elements include four strands of beta-pleated sheet and three alpha-helical regions.
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PMID:Crystallization and structure determination to 2.5-A resolution of the oxidized [2Fe-2S] ferredoxin isolated from Anabaena 7120. 190 76

Salivary proteins and glycoproteins that participate in the formation of 2-h in vivo enamel pellicle were determined utilizing polyacrylamide gel electrophoresis [sodium dodecyl sulphate (SDS)-PAGE and anionic PAGE]/Western transfer analyses, and specific radiolabelling/SDS-PAGE fluorography. The sensitivity of these methods permitted the identification of individual members of different salivary protein families. The major components of this pellicle were salivary alpha-amylase, cysteine-containing phosphoprotein (CCP or cystatins), salivary mucin and sIgA. Glycosylated amylase was present in larger quantity than the non-glycosylated species. Only CCP1 (cystatin SA-I) of the cysteine-containing phosphoprotein family was identified. The higher molecular-weight salivary mucin (MG1), but not the lower molecular-weight species (MG2), was detected. These results extend earlier observations regarding the selective nature of salivary protein adsorption to enamel surface by demonstrating that only specific members of salivary protein families are involved in 2-h in vivo enamel pellicle formation. The findings also suggest that individual family members may have different functions in the mouth.
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PMID:Characterization of in vivo salivary-derived enamel pellicle. 248 Jul 70

Sulphur is unique among the main elements of living cells in that it is covalently bound to biopolymers but does not occur in the biopolymer backbone. Indeed, most of the bacterial sulphur content resides in the methionine and cysteine side-chains of proteins. The growth yield of an organism under conditions of sulphur limitation could therefore be greatly enhanced by mutations that substitute Met and Cys in the organism's proteins for sulphur-free amino acids. Because the saving in sulphur would increase with such accumulating mutations, Met and Cys changes could be progressively selected. Abundant proteins should be the prime targets of such a selection. A few published observations give credence to this scenario. Sulphate permease, which is abundantly produced by sulphur-starved Salmonella typhimurium, lacks Met and Cys residues. Also, two species of marine purple bacteria synthesize more protein than can be expected from a limited sulphate supply. We now report that the cyanobacterium Calothrix sp. PCC 7601 (referred to here as Calothrix) encodes sulphur-depleted versions of its most abundant proteins--phycocyanin and its auxiliary polypeptides--which it specifically expresses under conditions of sulphur limitation. Although these proteins do not take part in the fixation of sulphur, their elevated synthesis affects the sulphur budget of cyanobacterial cells. Direct evidence is thus provided that the structure of macromolecules can be subject to metabolic optimization.
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PMID:Adaptive eradication of methionine and cysteine from cyanobacterial light-harvesting proteins. 250 52

Using the cysA locus of Salmonella typhimurium as a heterologous probe, we have cloned a region of the Anacystis nidulans R2 (Synechococcus PCC 7942) genome involved in sulfate assimilation. The 8.3-kilobase-pair region encodes at least five transcripts that cannot be detected unless the cells are deprived of sulfur. One of the genes in this region has been sequenced, and the protein that it encodes is homologous to a polypeptide component of other permease systems of Escherichia coli and Salmonella. Insertional inactivation of the putative sulfate permease gene, designated cysA, as well as of other genes within this region, results in cysteine auxotrophy, reduced sulfate uptake, and altered expression of soluble and cytoplasmic-membrane polypeptides associated with sulfur starvation.
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PMID:A region of a cyanobacterial genome required for sulfate transport. 253 23


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