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Báo cáo khoa học: A chloroplast RNA binding protein from stromal thylakoid membranes specifically binds to the 5¢ untranslated region of the psbA mRNA

The intrachloroplastic localization of post-transcriptional gene expression steps represents one key determinant for the regulation of chloroplast development. We have character-ized an RNA binding protein of 63kDa (RBP63) from Chlamydomonas reinhardtiichloroplasts, which cofraction-ates with stromal thylakoid membranes. Solubility proper-ties suggest that RBP63is a peripheral membrane protein. | Eur. J. Biochem. 269 3912-3919 2002 FEBS 2002 doi 10.1046 j.1432-1033.2002.03057.x A chloroplast RNA binding protein from stromal thylakoid membranes specifically binds to the 5 untranslated region of the psbA mRNA Friedrich Ossenbiihl Kristina Hartmann and Jorg Nickelsen Lehrstuhl fur Allgemeine und Molekulare Botanik Ruhr-Universitat Bochum Bochum Germany The intrachloroplastic localization of post-transcriptional gene expression steps represents one key determinant for the regulation of chloroplast development. We have characterized an RNA binding protein of 63 kDa RBP63 fimm Chlamydomonas reinhardtii chloroplasts which cofractionates with stromal thylakoid membranes. Solubility properties suggest that RBP63 is a eeil hesrnl membrane protein. Among RNA probes from different 5 untranslated regions of chloroplast transcripts RBP63 pi f I efeniallly binds to the psbA leader. This binding is dependent on a region comprising seven consecutive A residues which is required for D1 protein synthesis. A possible role for this newly discovered RNA binding protein in membrane targeting of psbA gene expression is discussed. Keywords chloroplast gene expression D1 synthesis membrane targeting RNA binding thylakoid. Chloroplast gene expression within plant or algal cells has been shown to be dependent upon nuclear gene products which are translated in the cytoplasm and subsequently are imported by the organelle. Herein they fulfil their function by interacting with distinct elements and or factors associated with the chloroplast gene expression machinery 1 2 . While the molecular mechanisms of regulatory interaction during these processes are being pieced together relatively little is known about the intrachloroplast localization of different steps of gene expression. For instance the chloroplast DNA is organized in nucleoids. In developing higher plants these are associated with the inner plastid envelope through the PEND protein. Upon full chloroplast maturation the cpDNA is