Abstract
Plastid nucleoid is a complex of platid DNA and various proteins, which changes morphologically and molecularly during the development of pea chloroplast. We reported that the 70-kDa protein, which is a major constituent of chloroplast nucleoid, was identified as sulfite reductase (SiR), and this protein has an ability to compact DNA. Tightening of DNA compaction by addition of recombinant SiR and its relaxation owing to release of SiR by heparin were confirmed. In vitro transcription assay using isolated nucleoids showed that the DNA compaction by SiR repressed, while DNA relaxation activated transcriptional activity. We will also present data on the DNA binding of SiR. A SiR-GFP fusion protein was found to localize in both stroma and nucleoids. We are attempting to identify DNA-binding domain of SiR.
