title: ATP stimulates signal recognition particle (SRP)/FtsY-supported protein integration in chloroplasts.
abstract: The signal recognition particle (SRP) and its receptor (FtsY in prokaryotes) are essential for cotranslational protein targeting to the endoplasmic reticulum in eukaryotes and the cytoplasmic membrane in prokaryotes. An SRP/FtsY-like protein targeting/integration pathway in chloroplasts mediates the posttranslational integration of the light-harvesting chlorophyll a/b-binding protein (LHCP) into thylakoid membranes. GTP, chloroplast SRP (cpSRP), and chloroplast FtsY (cpFtsY) are required for LHCP integration into thylakoid membranes. Here, we report the reconstitution of the LHCP integration reaction with purified recombinant proteins and salt-washed thylakoids. Our data demonstrate that cpSRP and cpFtsY are the only soluble protein components required for LHCP integration. In addition, our studies reveal that ATP, though not absolutely required, remarkably stimulates LHCP integration into salt-washed thylakoids. ATP stimulates LHCP integration by a mechanism independent of the thylakoidal pH gradient (DeltapH) and exerts no detectable effect on the formation of the soluble LHCP-cpSRP-targeting complex. Taken together, our results indicate the participation of a thylakoid ATP-binding protein in LHCP integration.
authors.affiliation: Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701, USA.
authors.forename: Jianguo
authors.initials: J
authors.lastname: Yuan
authors.forename: Alicia
authors.initials: A
authors.lastname: Kight
authors.forename: Robyn L
authors.initials: RL
authors.lastname: Goforth
authors.forename: Misty
authors.initials: M
authors.lastname: Moore
authors.forename: Eric C
authors.initials: EC
authors.lastname: Peterson
authors.forename: Joshua
authors.initials: J
authors.lastname: Sakon
authors.forename: Ralph
authors.initials: R
authors.lastname: Henry
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism*; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism*; D010957:Plasmids; D021382:Protein Sorting Signals / Q000502:physiology; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018271:Signal Recognition Particle / Q000378:metabolism*; D020524:Thylakoids / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; C087406:FtsY protein, Bacteria; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D021382:Protein Sorting Signals; D018160:Receptors, Cytoplasmic and Nuclear; D011994:Recombinant Proteins; D018271:Signal Recognition Particle; D000255:Adenosine Triphosphate