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

Thioredoxin is a small redox protein with an active-site disulfide/dithiol. The protein from Escherichia coli has been well characterized. The genes encoding thioredoxin in E. coli and in the filamentous cyanobacterium Anabaena PCC 7119 have been cloned and sequenced. Anabaena thioredoxin exhibits 50% amino acid identity with the E. coli protein and interacts with E. coli enzymes. The genes encoding Anabaena and E. coli thioredoxin were fused via a common restriction site in the nucleotide sequence coding for the active site of the proteins to generate hybrid genes, coding for two chimeric thioredoxins. These proteins are designated Anabaena-E. coli (A-E) thioredoxin for the construct with the Anabaena sequence from the N-terminus to the middle of the active site and the E. coli sequence to the C-terminus, and E. coli-Anabaena (E-A) for the opposite construct. The gene encoding the A-E thioredoxin complements all phenotypes of an E. coli thioredoxin-deficient strain, whereas the gene encoding E-A thioredoxin is only partially effective. Purified E-A thioredoxin exhibits a much lower catalytic efficiency with E. coli thioredoxin reductase and ribonucleotide reductase than either E. coli or Anabaena thioredoxin. In contrast, the A-E thioredoxin has a higher catalytic efficiency in these reactions than either parental protein. Reaction with antibodies to E. coli and Anabaena thioredoxins shows that the antigenic determinants for thioredoxin are located in the C-terminal part of the molecule and retain the native conformation in the hybrid proteins.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Characterization of Escherichia coli-Anabaena sp. hybrid thioredoxins. 313 96

A 245 GHz 8.7 T high-field EPR study of tyrosine-D (TyrD zero) and tyrosine-Z (TyrZ zero) radicals of photosystem II (PSII) from Synechocystis PCC 6803 was carried out. Identical principal g values for the wild-type Synechocystis and spinach TyrD zero showed that the two radicals were in similar electrostatic environments. By contrast, the principal g values of the TyrD zero in the D2-His189Gln mutant of Synechocystis were different from those of the wild-type and spinach radicals and were similar to those of the tyrosyl radical in ribonucleotide reductase. These comparisons indicate that the D2-His189Gln mutant TyrD zero is not hydrogen-bonded or is only weakly so. The HF-EPR spectrum of TyrZ zero was obtained from the D2-Tyr160Phe mutant that lacks TyrD zero. The principal g values were nearly identical to those of the wild-type TyrD zero. The low-field edge of the TyrZ zero spectrum was much broader than at the other two principal g values and was also much broader than the TyrD zero spectrum. From the identical g values and previous work on tyrosyl radical g values [Un S., Atta M., Fontecave, M., & Rutherford, A. W. (1995) J. Am. Chem. Soc. 117, 10713-10719], it was concluded that TyrZ zero, like TyrD zero, is hydrogen-bonded The broadness of the gx component was interpreted as a distribution in strength of the hydrogen-bonding due to disorder in the protein environment about TyrZ zero.
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PMID:245 GHz high-field EPR study of tyrosine-D zero and tyrosine-Z zero in mutants of photosystem II. 854 47

In Escherichia coli, flavodoxin is the physiological electron donor for the reductive activation of the enzymes pyruvate formate-lyase, anaerobic ribonucleotide reductase, and B12-dependent methionine synthase. As a basis for studies of the interactions of flavodoxin with methionine synthase, crystal structures of orthorhombic and trigonal forms of oxidized recombinant flavodoxin from E. coli have been determined. The orthorhombic form (space group P2(1)2(1)2(1), a = 126.4, b = 41.10, c = 69.15 A, with two molecules per asymmetric unit) was solved initially by molecular replacement at a resolution of 3.0 A, using coordinates from the structure of the flavodoxin from Synechococcus PCC 7942 (Anacystis nidulans). Data extending to 1.8-A resolution were collected at 140 K and the structure was refined to an Rwork of 0.196 and an Rfree of 0.250 for reflections with I > 0. The final model contains 3,224 non-hydrogen atoms per asymmetric unit, including 62 flavin mononucleotide (FMN) atoms, 354 water molecules, four calcium ions, four sodium ions, two chloride ions, and two Bis-Tris buffer molecules. The structure of the protein in the trigonal form (space group P312, a = 78.83, c = 52.07 A) was solved by molecular replacement using the coordinates from the orthorhombic structure, and was refined with all data from 10.0 to 2.6 A (R = 0.191; Rfree = 0.249). The sequence Tyr 58-Tyr 59, in a bend near the FMN, has so far been found only in the flavodoxins from E. coli and Haemophilus influenzae, and may be important in interactions of flavodoxin with its partners in activation reactions. The tyrosine residues in this bend are influenced by intermolecular contacts and adopt different orientations in the two crystal forms. Structural comparisons with flavodoxins from Synechococcus PCC 7942 and Anaebaena PCC 7120 suggest other residues that may also be critical for recognition by methionine synthase.
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PMID:A flavodoxin that is required for enzyme activation: the structure of oxidized flavodoxin from Escherichia coli at 1.8 A resolution. 941 2

The gene for ribonucleotide reductase from Anabaena sp. strain PCC 7120 was identified and expressed in Escherichia coli. This gene codes for a 1,172-amino-acid protein that contains a 407-amino-acid intein. The intein splices itself from the protein when it is expressed in E. coli, yielding an active ribonucleotide reductase of 765 residues. The mature enzyme was purified to homogeneity from E. coli extracts. Anabaena ribonucleotide reductase is a monomer with a molecular weight of approximately 88,000, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Superose 12 column chromatography. The enzyme reduces ribonucleotides at the triphosphate level and requires a divalent cation and a deoxyribonucleoside triphosphate effector. The enzyme is absolutely dependent on the addition of the cofactor, 5'-adenosylcobalamin. These properties are characteristic of the class II-type reductases. The cyanobacterial enzyme has limited sequence homology to other class II reductases; the greatest similarity (38%) is to the reductase from Lactobacillus leichmannii. In contrast, the Anabaena reductase shows over 90% sequence similarity to putative reductases found in genome sequences of other cyanobacteria, such as Nostoc punctiforme, Synechococcus sp. strain WH8102, and Prochlorococcus marinus MED4, suggesting that the cyanobacterial reductases form a closely related subset of the class II enzymes.
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PMID:Isolation of the gene for the B12-dependent ribonucleotide reductase from Anabaena sp. strain PCC 7120 and expression in Escherichia coli. 1242 42

Glutaredoxin (Grx), which has been found widely in bacteria, plant, and mammalian cells, is an electron carrier for ribonucleotide reductase and a general glutathione-disulfide reductase of importance for redox regulation. The open reading frame designated ssr2061 from cyanobacterium Synechocystis sp. PCC 6803 was found as a homologous gene coding for Grx. The amino acid sequence deduced from ssr2061 shares high identity with that of Grxs from other organisms. In the present study, the protein of Grx2061 encoded by ssr2061 was successfully overexpressed as soluble fraction in Escherichia coli BL21 (DE3). The recombinant protein was purified to near homogenity by two steps involving immobilized metal affinity chromatography and gel filtration chromatography with a yield of 22% and a specific activity of 41.5 micromol NADPH oxidized per milligram of protein in the 2-hydroxyethyl disulfide assay. The pET-2061 transformed Escherichia coli cells showed higher Grx activity and tolerance to H(2)O(2) mediated growth inhibition compared to cells transformed with the vector alone. This suggests that overexpression of Grx from Synechocystis sp. PCC 6803 may provide protection to E. coli cells against oxidative stress mediated by H(2)O(2).
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PMID:Expression and oxidative stress tolerance studies of glutaredoxin from cyanobacterium Synechocystis sp. PCC 6803 in Escherichia coli. 1588 49