title: Structure and dynamics of photosystem II light-harvesting complex revealed by high-resolution FTICR mass spectrometric proteome analysis.
abstract: Structure and dynamics of membrane-bound light-harvesting pigment-protein complexes (LHCs), which collect and transmit light energy for photosynthesis and thereby play an essential role in the regulation of photosynthesis and photoprotection, were identified and characterized using high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). LHCs from photosystem II (LHCII) were isolated from the thylakoid membrane of Arabidopsis thaliana leaves after light stress treatment using sucrose density gradient centrifugation, and separated by gel-filtration into LHCII subcomplexes. Using reversed-phase high-performance liquid chromatography and two-dimensional (2D) gel electrophoresis, the LHCII proteins, Lhcb1-6 and fibrillins, were efficiently separated and identified by FTICR-MS. Some of the LHCII subcomplexes were shown to migrate from photosystem II to photosystem I as a result of short-term adaptation to changes in light intensity. In the mobile LHCII subcomplexes, decreased levels of fibrillins and a modified composition of LHCII protein isoforms were identified compared to the tightly bound LHCII subcomplexes. In addition, FTICR-MS analysis revealed several oxidative modifications of LHCII proteins. A number of protein spots in 2D gels were found to contain a mixture of proteins, illustrating the feasibility of high-resolution mass spectrometry to identify proteins that remain unseparated in 2D gels even upon extended pH gradients.
authors.affiliation: Laboratory of Analytical Chemistry and Biopolymer Structure Analysis, Department of Chemistry, University of Konstanz, Konstanz, Germany.
authors.forename: Dmitry
authors.initials: D
authors.lastname: Galetskiy
authors.forename: Iuliana
authors.initials: I
authors.lastname: Susnea
authors.forename: Verena
authors.initials: V
authors.lastname: Reiser
authors.forename: Iwona
authors.initials: I
authors.lastname: Adamska
authors.forename: Michael
authors.initials: M
authors.lastname: Przybylski
mesh_terms: D017360:Arabidopsis / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry*; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry; D040901:Proteomics; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*
chemical_list: D029681:Arabidopsis Proteins; D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex; D010936:Plant Extracts