title: Anionic Phospholipids and the Albino3 Translocase Activate Signal Recognition Particle-Receptor Interaction during Light-harvesting Chlorophyll a/b-binding Protein Targeting.
abstract: The universally conserved signal recognition particle (SRP) co-translationally delivers newly synthesized membrane and secretory proteins to the target cellular membrane. The only exception is found in the chloroplast of green plants, where the chloroplast SRP (cpSRP) post-translationally targets light-harvesting chlorophyll a/b-binding proteins (LHCP) to the thylakoid membrane. The mechanism and regulation of this post-translational mode of targeting by cpSRP remain unclear. Using biochemical and biophysical methods, here we show that anionic phospholipids activate the cpSRP receptor cpFtsY to promote rapid and stable cpSRP54·cpFtsY complex assembly. Furthermore, the stromal domain of the Alb3 translocase binds with high affinity to and regulates GTP hydrolysis in the cpSRP54·cpFtsY complex, suggesting that cpFtsY is primarily responsible for initial recruitment of the targeting complex to Alb3. These results suggest a new model for the sequential recruitment, remodeling, and unloading of the targeting complex at membrane translocase sites in the post-translational cpSRP pathway.
authors.affiliation: From the Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125.
authors.forename: Sowmya
authors.initials: S
authors.lastname: Chandrasekar
authors.affiliation: From the Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125 sshan@caltech.edu.
authors.forename: Shu-Ou
authors.identifier: http://orcid.org/0000-0002-6526-1733
authors.initials: SO
authors.lastname: Shan
mesh_terms: D000595:Amino Acid Sequence; D000838:Anions; D017360:Arabidopsis / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D061146:Chlorophyll Binding Proteins / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism; D019143:Evolution, Molecular; D020558:GTP Phosphohydrolases / Q000378:metabolism; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism*; D010802:Phylogeny; D011485:Protein Binding; D011487:Protein Conformation; D021381:Protein Transport; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D018000:Receptors, Peptide / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D018271:Signal Recognition Particle / Q000378:metabolism*
chemical_list: C106404:ALBINO 3 protein, Arabidopsis; D000838:Anions; D029681:Arabidopsis Proteins; D061146:Chlorophyll Binding Proteins; D045342:Light-Harvesting Protein Complexes; D010743:Phospholipids; D018160:Receptors, Cytoplasmic and Nuclear; D018000:Receptors, Peptide; D018271:Signal Recognition Particle; C036318:signal peptide receptor; D020558:GTP Phosphohydrolases
keywords: GTPase; GTPases; chloroplast; phospholipid; protein targeting; signal recognition particle (SRP)