title: Rigid core and flexible terminus: structure of solubilized light-harvesting chlorophyll a/b complex (LHCII) measured by EPR.
abstract: The structure of the major light-harvesting chlorophyll a/b complex (LHCII) was analyzed by pulsed EPR measurements and compared with the crystal structure. Site-specific spin labeling of the recombinant protein allowed the measurement of distance distributions over several intra- and intermolecular distances in monomeric and trimeric LHCII, yielding information on the protein structure and its local flexibility. A spin label rotamer library based on a molecular dynamics simulation was used to take the local mobility of spin labels into account. The core of LHCII in solution adopts a structure very similar or identical to the one seen in crystallized LHCII trimers with little motional freedom as indicated by narrow distance distributions along and between α helices. However, distances comprising the lumenal loop domain show broader distance distributions, indicating some mobility of this loop structure. Positions in the hydrophilic N-terminal domain, upstream of the first trans-membrane α helix, exhibit more and more mobility the closer they are to the N terminus. The nine amino acids at the very N terminus that have not been resolved in any of the crystal structure analyses give rise to very broad and possibly bimodal distance distributions, which may represent two families of preferred conformations.
authors.affiliation: Institut für Allgemeine Botanik der Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Dockter
authors.forename: André H
authors.initials: AH
authors.lastname: Müller
authors.forename: Carsten
authors.initials: C
authors.lastname: Dietz
authors.forename: Aleksei
authors.initials: A
authors.lastname: Volkov
authors.forename: Yevhen
authors.initials: Y
authors.lastname: Polyhach
authors.forename: Gunnar
authors.initials: G
authors.lastname: Jeschke
authors.forename: Harald
authors.initials: H
authors.lastname: Paulsen
mesh_terms: D002734:Chlorophyll / Q000737:chemistry; D000077194:Chlorophyll A; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D018532:Pisum sativum / Q000201:enzymology*; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013113:Spin Labels
chemical_list: D045342:Light-Harvesting Protein Complexes; D013113:Spin Labels; D002734:Chlorophyll; C037184:chlorophyll b; D000077194:Chlorophyll A