title: Cardiolipin clusters and membrane domain formation induced by mitochondrial proteins.
abstract: We show in this study that mitochondrial creatine kinase promotes segregation and clustering of cardiolipin in mixed membranes, a phenomenon that has been proposed to occur at contact sites in the mitochondria. This property of mitochondrial creatine kinase is dependent on the native octameric structure of the protein and does not occur after heat-denaturation or with the native dimeric form of the protein. Cardiolipin segregation was demonstrated by differential scanning calorimetry using membranes containing cardiolipin and either dipalmitoylphosphatidylethanolamine or 1-palmitoyl-2-oleoylphosphatidylethanolamine. Addition of the ubiquitous form of mitochondrial creatine kinase leads to the formation of a phosphatidylethanolamine-rich domain as a result of the protein binding preferentially to the cardiolipin. Such phase separation does not occur if cardiolipin is replaced with dioleoyl phosphatidylglycerol. Lipid phase separation is observed with other cardiolipin-binding proteins, including cytochrome c and, to a very small extent, with truncated Bid (t-Bid), as well as with the cationic polypeptide poly-L-lysine, but among these proteins the octameric form of mitochondrial creatine kinase is by far the most effective in causing segregation and clustering of cardiolipin. The proteins included in this study are found at mitochondrial contact sites where they are known to associate with cardiolipin. Domains in mitochondria enriched in cardiolipin play an important role in apoptosis and in energy flux processes.
authors.affiliation: Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada L8N 3Z5.
authors.forename: Raquel F
authors.initials: RF
authors.lastname: Epand
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Tokarska-Schlattner
authors.forename: Uwe
authors.initials: U
authors.lastname: Schlattner
authors.forename: Theo
authors.initials: T
authors.lastname: Wallimann
authors.forename: Richard M
authors.initials: RM
authors.lastname: Epand
mesh_terms: D000818:Animals; D002152:Calorimetry, Differential Scanning; D002308:Cardiolipins / Q000737:chemistry* / Q000502:physiology*; D002942:Circular Dichroism; D052281:Creatine Kinase, Mitochondrial Form / Q000378:metabolism; D045304:Cytochromes c / Q000737:chemistry; D019281:Dimerization; D006801:Humans; D008055:Lipids / Q000737:chemistry; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000737:chemistry; D011107:Polylysine / Q000737:chemistry; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D013696:Temperature
chemical_list: D002308:Cardiolipins; D008055:Lipids; D024101:Mitochondrial Proteins; D011994:Recombinant Proteins; D011107:Polylysine; D045304:Cytochromes c; D052281:Creatine Kinase, Mitochondrial Form