- A-Z
- Endocytobiosis and ...
- Volume 24 (2013)
- Association of tran...
- Autor(in)
- Seitenbereich
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027-034
- Schlagwort(e)
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Chloroplasts, elongation factor Tu, plastid nucleoids, ptNAPs, transcriptionally active chromosomes
- Zusammenfsg.
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Chloroplast translation elongation factor EF-Tu is a predominantly stromal protein that has been associated with translation and protection of proteins towards thermal aggregation. A minor proportion of the protein with undetermined function was found in chloroplast membrane fractions. We show here that membrane-attached EF-Tu from spinach chloroplasts co-purifies with a biochemical fraction termed the “transcriptionally active chromosome” (TAC) which contains plastid DNA and exhibits endogenous transcriptional activity. Full length EF-Tu tagged with fluorescent marker proteins is distributed between a stromal fraction and punctate speckles along the intraplastidial membranes of chloroplasts in transiently transformed protoplasts. The deletion or masking of the plastid target peptide of EF-Tu resulted in a nucleo-cytoplasmic distribution of the protein. Speckle formation is typical for plastid nucleoid associated proteins, so we investigated the overlap of EF-Tu fluorescence with that of dsRed-tagged plastid envelope DNA binding protein (PEND) and dsRed-tagged plastid RNA-binding protein At-WHIRLY1. The speckles containing each protein overlapped sometimes but not always with each other, and frequently showed a partial overlap. This observation lends support for assumptions of a close association of different DNA- and RNA-related functions and may point to a heterogeneity of the nucleoid population within a single chloroplast.