title: Ribosome nascent chain complexes of the chloroplast-encoded cytochrome b6 thylakoid membrane protein interact with cpSRP54 but not with cpSecY.
abstract: We analysed the interplay between the cpSecY, cpSRP54 and the chloroplast-encoded cytochrome b6 via isolation of chloroplast ribosome nascent chain complexes and the use of cross-linking factors, antibodies and mass spectroscopy analyses. We showed that the cytochrome b6 nascent polypeptide complex is tightly associated with ribosomes and that the translation of cytochrome b6 was discontinuous. The causes of ribosome pausing and the functional significance of this phenomenon may be related to proper protein folding, insertion into thylakoid membranes and the association of cofactors during this process. It was also found that cpSecY was not in the vicinity of cytochrome b6 intermediates during the elongation process and does not act with mature cytochrome b6 after translation. Using the approach of cross-linking during elongation of the cytochrome b6 protein, we showed that cpSRP54 interacts strongly with the elongating nascent chain.
authors.affiliation: Faculty of Biotechnology, University of Wrocław, Fryderyka Joliot-Curie 14a, 50-383, Wroclaw, Poland.
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Piskozub
authors.forename: Bożena
authors.initials: B
authors.lastname: Króliczewska
authors.forename: Jarosław
authors.initials: J
authors.lastname: Króliczewski
mesh_terms: D029681:Arabidopsis Proteins / Q000378:metabolism; D015153:Blotting, Western; D060365:Chloroplast Proteins; D002736:Chloroplasts / Q000235:genetics* / Q000378:metabolism; D003432:Cross-Linking Reagents; D045347:Cytochromes b6 / Q000235:genetics / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D047468:Immunoprecipitation; D013058:Mass Spectrometry; D008565:Membrane Proteins / Q000378:metabolism; D018532:Pisum sativum / Q000235:genetics*; D014176:Protein Biosynthesis / Q000502:physiology*; D017510:Protein Folding; D011804:Quinolines; D012270:Ribosomes / Q000378:metabolism*; D000069816:SEC Translocation Channels; D018271:Signal Recognition Particle / Q000378:metabolism*; D020524:Thylakoids / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D060365:Chloroplast Proteins; D003432:Cross-Linking Reagents; D045347:Cytochromes b6; D008565:Membrane Proteins; D011804:Quinolines; C000613370:SCY1 protein, Arabidopsis; D000069816:SEC Translocation Channels; D018271:Signal Recognition Particle; C047117:bicinchoninic acid