title: Investigation of phycobilisome subunit interaction interfaces by coupled cross-linking and mass spectrometry.
abstract: The phycobilisome (PBS) is an extremely large light-harvesting complex, common in cyanobacteria and red algae, composed of rods and core substructures. These substructures are assembled from chromophore-bearing phycocyanin and allophycocyanin subunits, nonpigmented linker proteins and in some cases additional subunits. To date, despite the determination of crystal structures of isolated PBS components, critical questions regarding the interaction and energy flow between rods and core are still unresolved. Additionally, the arrangement of minor PBS components located inside the core cylinders is unknown. Different models of the general architecture of the PBS have been proposed, based on low resolution images from electron microscopy or high resolution crystal structures of isolated components. This work presents a model of the assembly of the rods onto the core arrangement and for the positions of inner core components, based on cross-linking and mass spectrometry analysis of isolated, functional intact Thermosynechococcus vulcanus PBS, as well as functional cross-linked adducts. The experimental results were utilized to predict potential docking interactions of different protein pairs. Combining modeling and cross-linking results, we identify specific interactions within the PBS subcomponents that enable us to suggest possible functional interactions between the chromophores of the rods and the core and improve our understanding of the assembly, structure, and function of PBS.
authors.affiliation: From the Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa, 32000, Israel and.
authors.forename: Ofir
authors.initials: O
authors.lastname: Tal
authors.affiliation: the Department of Biology, Faculty of Natural Sciences, University of Haifa at Oranim, 36006 Tivon, Israel.
authors.forename: Beny
authors.initials: B
authors.lastname: Trabelcy
authors.affiliation: the Department of Biology, Faculty of Natural Sciences, University of Haifa at Oranim, 36006 Tivon, Israel.
authors.forename: Yoram
authors.initials: Y
authors.lastname: Gerchman
authors.affiliation: From the Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa, 32000, Israel and nadir@tx.technion.ac.il.
authors.forename: Noam
authors.initials: N
authors.lastname: Adir
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D000458:Cyanobacteria / Q000201:enzymology*; D013058:Mass Spectrometry; D008958:Models, Molecular; D045524:Phycobilisomes / Q000737:chemistry* / Q000378:metabolism; D021122:Protein Subunits / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D045524:Phycobilisomes; D021122:Protein Subunits
keywords: Cyanobacteria; Energetics; Mass Spectrometry (MS); Molecular Modeling; Photosynthesis