title: ppGpp inhibits peptide elongation cycle of chloroplast translation system in vitro.
abstract: Chloroplasts possess common biosynthetic pathways for generating guanosine 3',5'-(bis)pyrophosphate (ppGpp) from GDP and ATP by RelA-SpoT homolog enzymes. To date, several hypothetical targets of ppGpp in chloroplasts have been suggested, but they remain largely unverified. In this study, we have investigated effects of ppGpp on translation apparatus in chloroplasts by developing in vitro protein synthesis system based on an extract of chloroplasts isolated from pea (Pisum sativum). The chloroplast extracts showed stable protein synthesis activity in vitro, and the activity was sensitive to various types of antibiotics. We have demonstrated that ppGpp inhibits the activity of chloroplast translation in dose-effective manner, as does the toxic nonhydrolyzable GTP analog guanosine 5'-(β,γ-imido)triphosphate (GDPNP). We further examined polyuridylic acid-directed polyphenylalanine synthesis as a measure of peptide elongation activity in the pea chloroplast extract. Both ppGpp and GDPNP as well as antibiotics, fusidic acid and thiostrepton, inhibited the peptide elongation cycle of the translation system, but GDP in the similar range of the tested ppGpp concentration did not affect the activity. Our results thus show that ppGpp directly affect the translation system of chloroplasts, as they do that of bacteria. We suggest that the role of the ppGpp signaling system in translation in bacteria is conserved in the translation system of chloroplasts.
authors: Division of Biomolecular Engineering, Cell-Free Science and Technology Research Center, Ehime University, Matsuyama, Ehime, Japan.
authors: Yuhta
authors: Y
authors: Nomura
authors: Taito
authors: T
authors: Takabayashi
authors: Hiroshi
authors: H
authors: Kuroda
authors: Yasushi
authors: Y
authors: Yukawa
authors: Kwanchanok
authors: K
authors: Sattasuk
authors: Mitsuru
authors: M
authors: Akita
authors: Akira
authors: A
authors: Nozawa
authors: Yuzuru
authors: Y
authors: Tozawa
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002250:Carbon Radioisotopes; D002736:Chloroplasts / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005672:Fusidic Acid / Q000494:pharmacology; D006153:Guanosine Diphosphate / Q000378:metabolism / Q000494:pharmacology; D006159:Guanosine Tetraphosphate / Q000378:metabolism* / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D007930:Leucine / Q000235:genetics / Q000378:metabolism; D018532:Pisum sativum / Q000235:genetics / Q000378:metabolism; D010441:Peptide Chain Elongation, Translational / Q000187:drug effects / Q000235:genetics*; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D011072:Poly U / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D013883:Thiostrepton / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D002250:Carbon Radioisotopes; C503923:GDPNP compound; D010455:Peptides; D010940:Plant Proteins; D012333:RNA, Messenger; D006153:Guanosine Diphosphate; D011072:Poly U; C012001:polyphenylalanine; D006159:Guanosine Tetraphosphate; D005672:Fusidic Acid; D006160:Guanosine Triphosphate; D007930:Leucine; D013883:Thiostrepton