Journal Article

Molecular Characterization and Redox Regulation of Phosphoribulokinase from the Cyanobacterium <i>Synechococcus</i> sp. PCC 7942

Daisuke Kobayashi, Masahiro Tamoi, Toshio Iwaki, Shigeru Shigeoka and Akira Wadano

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 44, issue 3, pages 269-276
Published in print March 2003 | ISSN: 0032-0781
Published online March 2003 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcg048
Molecular Characterization and Redox Regulation of Phosphoribulokinase from the Cyanobacterium Synechococcus sp. PCC 7942

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We isolated and characterized a gene encoding phosphoribulokinase (PRK) from Synechococcus sp. PCC 7942. The isolated sequence consisted of a 999 bp open reading frame encoding 333 amino acid residues of PRK. The PRK contained a pair of cysteinyl residues corresponding to Cys16 and Cys55 of spinach PRK regulated by a ferredoxin-thioredoxin system. However, there were seventeen amino acid residues lacking between the two cysteinyl residues compared with those of the chloroplastic enzyme in higher plants. The recombinant PRK of Synechococcus sp. PCC 7942 accounted for about 6–13% of the total soluble protein in the Escherichia coli. The specific activity of the enzyme was 230 µmol min–1 (mg protein)–1. The enzyme activity was completely inactivated by treatment with 5,5′-dithiobis (2-nitrobenzoic acid) (cysteinyl residue-specific oxidant) or was decreased by treatment with H2O2, but was more tolerant to oxidation than that of chloroplast. The oxidized PRK was fully activated by treatment with excessive dithiothreitol. Furthermore, incubation with 3 mM ATP protected the oxidation of the enzyme by either 5,5′-dithiobis (2-nitrobenzoic acid) or H2O2. These results suggest Synechococcus sp. PCC 7942 PRK can be regulated by reversible oxidation/reduction in vitro, but might be resistant to oxidative inactivation in vivo.

Keywords: Keywords: Phosphoribulokinase — Recombinant enzyme — Redox regulation — Synechococcus sp. PCC 7942.; The nucleotide sequence reported in this paper has been submitted to DDBJ under the accession number AB035257.

Journal Article.  5138 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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