title: Internal lipid architecture of the hetero-oligomeric cytochrome b6f complex.
abstract: The role of lipids in the assembly, structure, and function of hetero-oligomeric membrane protein complexes is poorly understood. The dimeric photosynthetic cytochrome b6f complex, a 16-mer of eight distinct subunits and 26 transmembrane helices, catalyzes transmembrane proton-coupled electron transfer for energy storage. Using a 2.5 Å crystal structure of the dimeric complex, we identified 23 distinct lipid-binding sites per monomer. Annular lipids are proposed to provide a connection for super-complex formation with the photosystem-I reaction center and the LHCII kinase enzyme for transmembrane signaling. Internal lipids mediate crosslinking to stabilize the domain-swapped iron-sulfur protein subunit, dielectric heterogeneity within intermonomer and intramonomer electron transfer pathways, and dimer stabilization through lipid-mediated intermonomer interactions. This study provides a complete structure analysis of lipid-mediated functions in a multi-subunit membrane protein complex and reveals lipid sites at positions essential for assembly and function.
authors.affiliation: Department of Biological Sciences, Hockmeyer Hall of Structural Biology, Purdue University, West Lafayette, IN 47907, USA. Electronic address: syedsaifhasan@gmail.com.
authors.forename: S Saif
authors.initials: SS
authors.lastname: Hasan
authors.affiliation: Department of Biological Sciences, Hockmeyer Hall of Structural Biology, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: William A
authors.initials: WA
authors.lastname: Cramer
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D045346:Cytochrome b6f Complex / Q000737:chemistry* / Q000378:metabolism; D004579:Electron Transport; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000378:metabolism; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry / Q000378:metabolism; D046911:Macromolecular Substances / Q000737:chemistry / Q000378:metabolism; D008563:Membrane Lipids / Q000737:chemistry* / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D046937:Nostoc / Q000378:metabolism; D045331:Photosystem I Protein Complex / Q000737:chemistry / Q000378:metabolism; D011494:Protein Kinases / Q000737:chemistry / Q000378:metabolism; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D007506:Iron-Sulfur Proteins; D045342:Light-Harvesting Protein Complexes; D046911:Macromolecular Substances; D008563:Membrane Lipids; D008565:Membrane Proteins; D045331:Photosystem I Protein Complex; D021122:Protein Subunits; D045346:Cytochrome b6f Complex; D011494:Protein Kinases; C120337:light-harvesting complex II kinase