title: Exploring the structure of the 100 amino-acid residue long N-terminus of the plant antenna protein CP29.
abstract: The structure of the unusually long (∼100 amino-acid residues) N-terminal domain of the light-harvesting protein CP29 of plants is not defined in the crystal structure of this membrane protein. We studied the N-terminus using two electron paramagnetic resonance (EPR) approaches: the rotational diffusion of spin labels at 55 residues with continuous-wave EPR, and three sets of distances with a pulsed EPR method. The N-terminus is relatively structured. Five regions that differ considerably in their dynamics are identified. Two regions have low rotational diffusion, one of which shows α-helical character suggesting contact with the protein surface. This immobile part is flanked by two highly dynamic, unstructured regions (loops) that cover residues 10-22 and 82-91. These loops may be important for the interaction with other light-harvesting proteins. The region around residue 4 also has low rotational diffusion, presumably because it attaches noncovalently to the protein. This section is close to a phosphorylation site (Thr-6) in related proteins, such as those encoded by the Lhcb4.2 gene. Phosphorylation might influence the interaction with other antenna complexes, thereby regulating the supramolecular organization in the thylakoid membrane.
authors.affiliation: Department of Molecular Physics, Leiden University, Leiden, The Netherlands.
authors.forename: Maryam Hashemi
authors.initials: MH
authors.lastname: Shabestari
authors.affiliation: Laboratory of Biophysics, Wageningen University, Wageningen, The Netherlands.
authors.forename: Cor J A M
authors.initials: CJ
authors.lastname: Wolfs
authors.affiliation: Laboratory of Biophysics, Wageningen University, Wageningen, The Netherlands.
authors.forename: Ruud B
authors.initials: RB
authors.lastname: Spruijt
authors.affiliation: Laboratory of Biophysics, Wageningen University, Wageningen, The Netherlands. Electronic address: huber@physics.leidenuniv.nl.
authors.forename: Herbert
authors.initials: H
authors.lastname: van Amerongen
authors.affiliation: Department of Molecular Physics, Leiden University, Leiden, The Netherlands. Electronic address: huber@physics.leidenuniv.nl.
authors.forename: Martina
authors.initials: M
authors.lastname: Huber
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000737:chemistry; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics; D060365:Chloroplast Proteins / Q000737:chemistry* / Q000235:genetics; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D009154:Mutation; D017434:Protein Structure, Tertiary; D012261:Ribonucleoproteins / Q000737:chemistry* / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D060365:Chloroplast Proteins; C529074:RBP29 protein, Arabidopsis; D012261:Ribonucleoproteins