title: Identification of protein stability determinants in chloroplasts.
abstract: Although chloroplast protein stability has long been recognised as a major level of post-translational regulation in photosynthesis and gene expression, the factors determining protein stability in plastids are largely unknown. Here, we have identified stability determinants in vivo by producing plants with transgenic chloroplasts that express a reporter protein whose N- and C-termini were systematically modified. We found that major stability determinants are located in the N-terminus. Moreover, testing of all 20 amino acids in the position after the initiator methionine revealed strong differences in protein stability and indicated an important role of the penultimate N-terminal amino acid residue in determining the protein half life. We propose that the stability of plastid proteins is largely determined by three factors: (i) the action of methionine aminopeptidase (the enzyme that removes the initiator methionine and exposes the penultimate N-terminal amino acid residue), (ii) an N-end rule-like protein degradation pathway, and (iii) additional sequence determinants in the N-terminal region.
authors.affiliation: Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476 Potsdam-Golm, Germany.
authors.forename: Wiebke
authors.initials: W
authors.lastname: Apel
authors.forename: Waltraud X
authors.initials: WX
authors.lastname: Schulze
authors.forename: Ralph
authors.initials: R
authors.lastname: Bock
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000235:genetics / Q000378:metabolism; D000626:Aminopeptidases / Q000378:metabolism; D002736:Chloroplasts / Q000235:genetics / Q000378:metabolism*; D003545:Cysteine / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006639:Histidine / Q000235:genetics / Q000378:metabolism; D063208:Methionyl Aminopeptidases; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D014176:Protein Biosynthesis; D055550:Protein Stability; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D000596:Amino Acids; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D012269:Ribosomal Proteins; D049452:Green Fluorescent Proteins; D006639:Histidine; D000626:Aminopeptidases; D063208:Methionyl Aminopeptidases; D003545:Cysteine