Interaction of a plant 14-3-3 protein with the signal peptide of a thylakoid-targeted chloroplast precursor protein and the presence of 14-3-3 isoforms in the chloroplast stroma.
The 14-3-3 proteins are acidic, dimeric proteins that have been implicated in many eukaryotic cellular processes because of direct protein association with enzymes and other metabolic and regulatory proteins. 14-3-3 proteins are largely considered to be cytoplasmic, but a search for proteins that specifically interact with a plant 14-3-3 resulted in the isolation of a nuclear-encoded, thylakoid-targeted chloroplast precursor, the full-length Arabidopsis photosystem I N-subunit At pPSI-N (P.C. Sehnke, R.J. Ferl ¿1995 Plant Physiol 109: 1126). Using precursor truncations in the two-hybrid system, it was determined that the leader sequence is the site of PSI-N that associates with 14-3-3. This suggested the novel possibility that 14-3-3 would be found within chloroplasts. Immuno-electron microscopy of leaf tissue and western analysis of chloroplast fractions with monoclonal anti-14-3-3 antibodies localized 14-3-3 proteins to the chloroplast stroma and the stromal side of thylakoid membranes. Using peptide-generated, isoform-specific antibodies, GF14nu, GF14epsilon, GF14mu, and GF14upsilon were shown to be present in the chloroplast stromal extract. These isoforms represent two distinct phylogenetic 14-3-3 groupings. These data suggest a novel interorganellar role for these phylogenetically distinct 14-3-3 proteins.
Sehnke
P C
PC
Program in Plant Molecular and Cellular Biology, Department of Horticultural Sciences, University of Florida, Gainesville, Florida 32611, USA.
Henry
R
R
Cline
K
K
Ferl
R J
RJ
D048948:14-3-3 Proteins; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism* / Q000648:ultrastructure; D008969:Molecular Sequence Data; D018532:Pisum sativum / Q000378:metabolism; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism; D045331:Photosystem I Protein Complex; D010940:Plant Proteins / Q000378:metabolism*; D011485:Protein Binding; D011498:Protein Precursors / Q000378:metabolism*; D021382:Protein Sorting Signals / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D020524:Thylakoids / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D014446:Tyrosine 3-Monooxygenase
D048948:14-3-3 Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D010940:Plant Proteins; D011498:Protein Precursors; D021382:Protein Sorting Signals; D011506:Proteins; D014446:Tyrosine 3-Monooxygenase