TAILIEUCHUNG - Báo cáo khoa học: DNA binding and partial nucleoid localization of the chloroplast stromal enzyme ferredoxin:sulfite reductase

Sulfite reductase (SiR) is an important enzyme catalyzing the reduction of sulfite to sulfide during sulfur assimilation in plants. This enzyme is locali-zed in plastids, including chloroplasts, and uses ferredoxin as an electron donor. Ferredoxin-dependent SiR has been found in isolated chloroplast nucleoids, but its localization in vivo or in intact plastids has not been examined. | ễFEBS Journal DNA binding and partial nucleoid localization of the chloroplast stromal enzyme ferredoxinzsulfite reductase Kohsuke Sekine1 2 Makoto Fujiwara2 Masato Nakayama3 Toshifumi Takao3 Toshiharu Hase3 and Naoki Sato1 2 1 Department of Molecular Biology Faculty of Science Saitama University Japan 2 Department of Life Sciences Graduate Schoolof Arts and Sciences The University of Tokyo Japan 3 Institute for Protein Research Osaka University Japan Keywords bifunctional protein chloroplast nucleoid DNA-binding protein ferredoxin sulfite reductase Correspondence N. Sato Department of Life Sciences Graduate Schoolof Arts and Sciences University of Tokyo 3-8-1 Komaba Meguro-ku Tokyo 153-8902 Japan Fax 81 3 5454699 Tel 81 3 54546631 E-mail naokisat@ Note Nucleotide sequence data for PsSiR are available in the DDBJ EMBL GenBank databases under accession number AB168112 Received 1 December 2006 revised 15 February 2007 accepted 19 February 2007 doi Sulfite reductase SiR is an important enzyme catalyzing the reduction of sulfite to sulfide during sulfur assimilation in plants. This enzyme is localized in plastids including chloroplasts and uses ferredoxin as an electron donor. Ferredoxin-dependent SiR has been found in isolated chloroplast nucleoids but its localization in vivo or in intact plastids has not been examined. Here we report the DNA-binding properties of SiRs from pea PsSiR and maize ZmSiR using an enzymatically active holoenzyme with prosthetic groups. PsSiR binds to both double-stranded and single-stranded DNA without significant sequence specificity. DNA binding did not affect the enzymatic activity of PsSiR suggesting that ferredoxin and sulfite are accessible to SiR molecules within the nucleoids. Comparison of PsSiR and ZmSiR suggests that ZmSiR does indeed have DNA-binding activity as was reported previously but the DNA affinity and DNA-compacting ability are higher in PsSiR than in ZmSiR. The tight

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