title: Modeling of the N-terminal Section and the Lumenal Loop of Trimeric Light Harvesting Complex II (LHCII) by Using EPR.
abstract: The major light harvesting complex II (LHCII) of green plants plays a key role in the absorption of sunlight, the regulation of photosynthesis, and in preventing photodamage by excess light. The latter two functions are thought to involve the lumenal loop and the N-terminal domain. Their structure and mobility in an aqueous environment are only partially known. Electron paramagnetic resonance (EPR) has been used to measure the structure of these hydrophilic protein domains in detergent-solubilized LHCII. A new technique is introduced to prepare LHCII trimers in which only one monomer is spin-labeled. These heterogeneous trimers allow to measure intra-molecular distances within one LHCII monomer in the context of a trimer by using double electron-electron resonance (DEER). These data together with data from electron spin echo envelope modulation (ESEEM) allowed to model the N-terminal protein section, which has not been resolved in current crystal structures, and the lumenal loop domain. The N-terminal domain covers only a restricted area above the superhelix in LHCII, which is consistent with the "Velcro" hypothesis to explain thylakoid grana stacking (Standfuss, J., van Terwisscha Scheltinga, A. C., Lamborghini, M., and Kühlbrandt, W. (2005) EMBO J. 24, 919-928). The conformation of the lumenal loop domain is surprisingly different between LHCII monomers and trimers but not between complexes with and without neoxanthin bound.
authors: From the Department of General Botany, Johannes Gutenberg-University, 55128 Mainz, Germany and.
authors: Niklas
authors: N
authors: Fehr
authors: From the Department of General Botany, Johannes Gutenberg-University, 55128 Mainz, Germany and.
authors: Carsten
authors: C
authors: Dietz
authors: the Department of Physical Chemistry, ETH Zürich, Vladimir Prelog-Weg 2, CH-8093 Zürich, Switzerland.
authors: Yevhen
authors: Y
authors: Polyhach
authors: the Department of Physical Chemistry, ETH Zürich, Vladimir Prelog-Weg 2, CH-8093 Zürich, Switzerland.
authors: Tona
authors: T
authors: von Hagens
authors: the Department of Physical Chemistry, ETH Zürich, Vladimir Prelog-Weg 2, CH-8093 Zürich, Switzerland.
authors: Gunnar
authors: G
authors: Jeschke
authors: From the Department of General Botany, Johannes Gutenberg-University, 55128 Mainz, Germany and paulsen@uni-mainz.de.
authors: Harald
authors: H
authors: Paulsen
mesh_terms: D001704:Biopolymers / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D008956:Models, Chemical; D008958:Models, Molecular; D045332:Photosystem II Protein Complex / Q000737:chemistry*; D011487:Protein Conformation
chemical_list: D001704:Biopolymers; D045332:Photosystem II Protein Complex
keywords: LHCII; N -terminus; electron paramagnetic resonance (EPR); light-harvesting complex (antenna complex); lumenal loop; membrane protein; molecular modeling; protein structure