title: Role of phospholipids in respiratory cytochrome bc(1) complex catalysis and supercomplex formation.
abstract: Specific protein-lipid interactions have been identified in X-ray structures of membrane proteins. The role of specifically bound lipid molecules in protein function remains elusive. In the current study, we investigated how phospholipids influence catalytic, spectral and electrochemical properties of the yeast respiratory cytochrome bc(1) complex and how disruption of a specific cardiolipin binding site in cytochrome c(1) alters respiratory supercomplex formation in mitochondrial membranes. Purified yeast cytochrome bc(1) complex was treated with phospholipase A(2). The lipid-depleted enzyme was stable but nearly catalytically inactive. The absorption maxima of the reduced b-hemes were blue-shifted. The midpoint potentials of the b-hemes of the delipidated complex were shifted from -52 to -82 mV (heme b(L)) and from +113 to -2 mV (heme b(H)). These alterations could be reversed by reconstitution of the delipidated enzyme with a mixture of asolectin and cardiolipin, whereas addition of the single components could not reverse the alterations. We further analyzed the role of a specific cardiolipin binding site (CL(i)) in supercomplex formation by site-directed mutagenesis and BN-PAGE. The results suggested that cardiolipin stabilizes respiratory supercomplex formation by neutralizing the charges of lysine residues in the vicinity of the presumed interaction domain between cytochrome bc(1) complex and cytochrome c oxidase. Overall, the study supports the idea, that enzyme-bound phospholipids can play an important role in the regulation of protein function and protein-protein interaction.
authors.affiliation: Max Planck Institute of Biophysics, Department of Molecular Membrane Biology, D-60438 Frankfurt, Germany.
authors.forename: Tina
authors.initials: T
authors.lastname: Wenz
authors.forename: Ruth
authors.initials: R
authors.lastname: Hielscher
authors.forename: Petra
authors.initials: P
authors.lastname: Hellwig
authors.forename: Hermann
authors.initials: H
authors.lastname: Schägger
authors.forename: Sebastian
authors.initials: S
authors.lastname: Richers
authors.forename: Carola
authors.initials: C
authors.lastname: Hunte
mesh_terms: D002308:Cardiolipins / Q000378:metabolism; D020134:Catalytic Domain / Q000235:genetics; D004563:Electrochemistry; D014450:Electron Transport Complex III / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004795:Enzyme Stability; D006418:Heme / Q000737:chemistry; D008928:Mitochondria / Q000378:metabolism; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D054467:Phospholipases A2; D010743:Phospholipids / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D013053:Spectrophotometry
chemical_list: D002308:Cardiolipins; D010743:Phospholipids; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D006418:Heme; D054467:Phospholipases A2; D014450:Electron Transport Complex III