title: The membrane-binding motif of the chloroplast signal recognition particle receptor (cpFtsY) regulates GTPase activity.
abstract: The chloroplast signal recognition particle (cpSRP) and its receptor (cpFtsY) function in thylakoid biogenesis to target integral membrane proteins to thylakoids. Unlike cytosolic SRP receptors in eukaryotes, cpFtsY partitions between thylakoid membranes and the soluble stroma. Based on sequence alignments, a membrane-binding motif identified in Escherichia coli FtsY appears to be conserved in cpFtsY, yet whether the proposed motif is responsible for the membrane-binding function of cpFtsY has yet to be shown experimentally. Our studies show that a small N-terminal region in cpFtsY stabilizes a membrane interaction critical to cpFtsY function in cpSRP-dependent protein targeting. This membrane-binding motif is both necessary and sufficient to direct cpFtsY and fused passenger proteins to thylakoids. Our results demonstrate that the cpFtsY membrane-binding motif may be functionally replaced by the corresponding region from E. coli, confirming that the membrane-binding motif is conserved among organellar and prokaryotic homologs. Furthermore, the capacity of cpFtsY for lipid binding correlates with liposome-induced GTP hydrolysis stimulation. Mutations that debilitate the membrane-binding motif in cpFtsY result in higher rates of GTP hydrolysis, suggesting that negative regulation is provided by the intact membrane-binding region in the absence of a bilayer. Furthermore, NMR and CD structural studies of the N-terminal region and the analogous region in the E. coli SRP receptor revealed a conformational change in secondary structure that takes place upon lipid binding. These studies suggest that the cpFtsY membrane-binding motif plays a critical role in the intramolecular communication that regulates cpSRP receptor functions at the membrane.
authors.affiliation: Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas 72701, USA.
authors.forename: Naomi J
authors.initials: NJ
authors.lastname: Marty
authors.forename: Dakshinamurthy
authors.initials: D
authors.lastname: Rajalingam
authors.forename: Alicia D
authors.initials: AD
authors.lastname: Kight
authors.forename: Nathaniel E
authors.initials: NE
authors.lastname: Lewis
authors.forename: Daniel
authors.initials: D
authors.lastname: Fologea
authors.forename: Thallapuranam Krishnaswamy Suresh
authors.initials: TK
authors.lastname: Kumar
authors.forename: Ralph L
authors.initials: RL
authors.lastname: Henry
authors.forename: Robyn L
authors.initials: RL
authors.lastname: Goforth
mesh_terms: D000409:Alanine / Q000378:metabolism; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism; D060365:Chloroplast Proteins; D002736:Chloroplasts / Q000201:enzymology*; D002942:Circular Dichroism; D004926:Escherichia coli; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D006868:Hydrolysis; D007425:Intracellular Membranes / Q000201:enzymology*; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism; D008051:Lipid Bilayers / Q000378:metabolism; D008081:Liposomes / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D008969:Molecular Sequence Data; D009711:Nucleotides / Q000378:metabolism; D018532:Pisum sativum; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D010649:Phenylalanine / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D013329:Structure-Activity Relationship; D020524:Thylakoids / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; D060365:Chloroplast Proteins; C087406:FtsY protein, Bacteria; D045342:Light-Harvesting Protein Complexes; D008051:Lipid Bilayers; D008081:Liposomes; D008565:Membrane Proteins; D009711:Nucleotides; D010455:Peptides; D018160:Receptors, Cytoplasmic and Nuclear; C513946:cpFtsY protein, Arabidopsis; D010649:Phenylalanine; D020558:GTP Phosphohydrolases; D000409:Alanine