title: Sycamore amyloplasts can import and process precursors of nuclear encoded chloroplast proteins.
abstract: Amyloplasts isolated from white-wild suspension-cultured cells of sycamore (Acer pseudoplatanus L.) are found to import and process the precursor of the small subunit (pS) of ribulose-1,5-bisphosphate carboxylase/oxygenase of spinach, but they lack the ability to form its holoenzyme due to the absence of both the large subunit and its binding-protein. They also import the precursor of the 33-kDa extrinsic protein (p33-kDa) of the O2-evolving complex of Photosystem II from spinach, but process is only to an intermediate form (i33-kDa). Chloroplasts from green-mutant cells of sycamore process p33-kDa to its mature form in this heterologous system. These results suggest that the thylakoid-associated protease responsible for the second processing step of p33-kDa is missing in amyloplasts, possibly due to the absence of thylakoid-membranes. In contrast, the apparent import of the precursor of the light-harvesting chlorophyll a/b-binding apoprotein (pLHCP) from spinach was not detected. Sycamore amyloplasts may lack the ability to import this particular thylakoid-protein, or rapidly degrade the imported molecules in the absence of thylakoid-membranes for their proper insertion.
authors.affiliation: Research Institute for Biochemical Regulation, School of Agriculture, Nagoya University, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Strzalka
authors.forename: J
authors.initials: J
authors.lastname: Ngernprasirtsiri
authors.forename: A
authors.initials: A
authors.lastname: Watanabe
authors.forename: T
authors.initials: T
authors.lastname: Akazawa
mesh_terms: D002734:Chlorophyll / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism*; D045342:Light-Harvesting Protein Complexes; D008565:Membrane Proteins / Q000378:metabolism; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism*; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism
chemical_list: D045342:Light-Harvesting Protein Complexes; D008565:Membrane Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D011498:Protein Precursors; C021261:thylakoid polypeptides; D002734:Chlorophyll; D012273:Ribulose-Bisphosphate Carboxylase