Control of protein life-span by N-terminal methionine excision.
Peptide deformylases (PDFs) have been discovered recently in eukaryotic genomes, and it appears that N-terminal methionine excision (NME) is a conserved pathway in all compartments where protein synthesis occurs. This work aimed at uncovering the function(s) of NME in a whole proteome, using the chloroplast-encoded proteins of both Arabidopsis thaliana and Chlamydomonas reinhardtii as model systems. Disruption of PDF1B in A.thaliana led to an albino phenotype, and an extreme sensitivity to the PDF- specific inhibitor actinonin. In contrast, a knockout line for PDF1A exhibited no apparent phenotype. Photosystem II activity in C.reinhardtii cells was substantially reduced by the presence of actinonin. Pulse-chase experiments revealed that PDF inhibition leads to destabilization of a crucial subset of chloroplast-encoded photosystem II components in C. reinhardtii. The same proteins were destabilized in pdf1b. Site-directed substitutions altering NME of the most sensitive target, subunit D2, resulted in similar effects. Thus, plastid NME is a critical mechanism specifically influencing the life-span of photosystem II polypeptides. A general role of NME in modulating the half-life of key subsets of proteins is suggested.
Giglione
Carmela
C
Protein Maturation, Trafficking and Signaling, UPR2355, Centre National de la Recherche Scientifique, Institut des Sciences du Végétal, Gif-sur-Yvette, France.
Vallon
Olivier
O
Meinnel
Thierry
T
D000581:Amidohydrolases; D000626:Aminopeptidases / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D017360:Arabidopsis / Q000201:enzymology*; D016825:Chlamydomonas reinhardtii / Q000201:enzymology*; D002736:Chloroplasts / Q000201:enzymology; D004795:Enzyme Stability; D007700:Kinetics; D008715:Methionine; D008954:Models, Biological; D016254:Mutagenesis, Insertional; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism; D045332:Photosystem II Protein Complex; D018087:Plastids / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017384:Sequence Deletion
D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D011994:Recombinant Proteins; D008715:Methionine; D000626:Aminopeptidases; D000581:Amidohydrolases; C084507:peptide deformylase