Poster: Organelle Biogenesis
Abs #
1128: Mitochondria and Chloroplasts Contain Their Own Systems for Iron-Sulfur Cluster Biosynthesis in Plant Cells
|
|
Presenter: |
Yabe, Toshiki , tyabe@protein.osaka-u.ac.jp |
Authors | Yabe, Toshiki (A) Kikuchi, Shingo (A) Nishio, Kazuaki (B) Morimoto, Kozo (A) Nakai, Masato (A) | | Affiliations: |
(A): Institute for Protein Research, Osaka University
(B): The Institute of Scientific and Industrial Research, Osaka University
|
|
|
Most recent identification of Isc/Nif proteins involved in Fe-S cluster biosynthesis has been carried out using some bacteria, yeast, and mammals, but not plastid-containing cells. Earlier studies suggested the presence of Fe-S cluster biosynthetic activity in higher plant chloroplasts. However no components actually involved in the activity have been identified so far. Recent genome and cDNA sequencing projects in several plants, most notably in Arabidopsis, have generated a great wealth of information that can provide working hypothesis to elucidate the detailed molecular mechanisms of Fe-S cluster biosynthesis in plants. We report here first characterization and future prospect on molecular crew participating assembly and delivery of Fe-S clusters in plant cells.
At first, we performed homology search with known bacterial Isc/Nif protein sequences against the entire genomic and EST databases of Arabidopsis. A number of Isc/Nif homologues were identified, and most of them contained amino-terminal extensions that seemed to serve as a targeting sequence either for mitochondria or chloroplasts. To determine subcellular localization of these Isc/Nif homologues, we carried out in vitro import study and Western analysis. The obtained data clearly suggest that both mitochondria and chloroplasts contain their own set of essential components for Fe-S cluster biosynthesis. Particularly, chloroplasts contain three NifU-like proteins whose cyanobacterial homologue has been proposed to serve as an essential scaffold protein for Fe-S cluster assembly and delivery. We will present detailed biochemical characterization of the chloroplastic NifU-like proteins that also show remarkable features as a scaffold protein for Fe-S cluster biosynthesis.
