title: The interaction between tBid and cardiolipin or monolysocardiolipin.
abstract: Bid, a BH3-only pro-apoptotic member of the Bcl-2 family, is cleaved by caspase 8 in apoptosis induced by death domain receptors. The carboxyl terminus of the cleavage product, tBid, remains associated with the amino terminal fragment (nBid) after cleavage. Dissociation of tBid from nBid occurs during targeting of tBid to mitochondria. We use an in vitro system and demonstrate that cardiolipin is sufficient for the dissociation. Monolysocardiolipin, a metabolite of cardiolipin that increases in mitochondria during apoptosis, has the same affinity to tBid as cardiolipin and is also capable of inducing dissociation of tBid from nBid. In contrast, phosphatidylethanolamine could not induce dissociation of tBid from nBid. To determine the site of tBid that interacts with cardiolipin, we performed mutational analysis by eliminating the positive-charged residues in helices 4-6. None of the single mutations can abolish the ability of tBid to target to mitochondria and to induce cytochrome c release, suggesting that positive-charged residues in helices 4-6 may not be required for mitochondrial targeting of tBid.
authors.affiliation: Huntsman Cancer Institute and Department of Internal Medicine, University of Utah, Salt Lake City, UT 84112, USA.
authors.forename: Jihua
authors.initials: J
authors.lastname: Liu
authors.forename: David
authors.initials: D
authors.lastname: Durrant
authors.forename: Hung-Sheng
authors.initials: HS
authors.lastname: Yang
authors.forename: Yongwen
authors.initials: Y
authors.lastname: He
authors.forename: Francis G
authors.initials: FG
authors.lastname: Whitby
authors.forename: David G
authors.initials: DG
authors.lastname: Myszka
authors.forename: Ray M
authors.initials: RM
authors.lastname: Lee
mesh_terms: D051023:BH3 Interacting Domain Death Agonist Protein; D001665:Binding Sites; D002308:Cardiolipins / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D053181:Caspase 8; D020169:Caspases / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D050356:Lipid Metabolism; D008246:Lysophospholipids / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D017433:Protein Structure, Secondary; D055672:Static Electricity
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D002308:Cardiolipins; D002352:Carrier Proteins; D008246:Lysophospholipids; C067188:monolysocardiolipin; D045304:Cytochromes c; C505530:CASP8 protein, human; D053181:Caspase 8; D020169:Caspases