title: Cardiolipin, phosphatidylserine, and BH4 domain of Bcl-2 family regulate Ca2+/H+ antiporter activity of human Bax inhibitor-1.
abstract: We investigated the effects of phospholipid composition in membranes and Bcl-2 homology (BH) domains of the Bcl-2 family on Ca2+/H+ antiporter activity of human recombinant Bax inhibitor-1 (BI-1) reconstituted into membranes. Cardiolipin (CL) and phosphatidylserine (PS) stimulated the proton-mediated efflux of Ca2+ ions encapsulated into proteoliposomes when compared to Ca2+ efflux from 100% phosphatidylcholine (PC) membranes in a CL or PS concentration-dependent manner. Concomitantly, the anionic phospholipids also enhanced H+ ion influx into the membranes. Lateral segregations of CL and PS were observed through the fluorescence properties of fluorophore-labeled phospholipids upon BI-1 reconstitution in PC/CL or PC/PS binary systems. However, other anionic phospholipids, such as phosphatidic acid, phosphatidylglycerol, and phosphatidylinositol did not influence the stimulation of BI-1 functions in membranes. The peptide corresponding to the BH4 domain of Bcl-2 and Bcl-xL proteins stimulated the BI-1 activities in 100% PC membranes. The peptide also showed an additive effect with CL or PS. Furthermore, the CL, PS, and BH4 domains specifically increased oligomerization levels such as dimer and tetramer of BI-1 in membranes. Taken together, these results suggest that the CL, PS, and BH4 domains were stimulating factors for the Ca2+/H+ antiporter activities of BI-1 through protein oligomerization.
authors.affiliation: Department of Biochemistry, College of Veterinary Medicine, Chonnam National University, Gwangju 500-757, Republic of Korea. thahn@chonnam.ac.kr
authors.forename: Taeho
authors.initials: T
authors.lastname: Ahn
authors.forename: Chul-Ho
authors.initials: CH
authors.lastname: Yun
authors.forename: Hyung-Ryong
authors.initials: HR
authors.lastname: Kim
authors.forename: Han-Jung
authors.initials: HJ
authors.lastname: Chae
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects; D002308:Cardiolipins / Q000378:metabolism*; D002417:Cattle; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D017136:Ion Transport / Q000187:drug effects; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008567:Membranes, Artificial; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism; D010718:Phosphatidylserines / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism; D011485:Protein Binding; D015202:Protein Engineering; D055503:Protein Multimerization / Q000187:drug effects; D017434:Protein Structure, Tertiary / Q000235:genetics; D011510:Proteolipids
chemical_list: D051017:Apoptosis Regulatory Proteins; D002308:Cardiolipins; D008565:Membrane Proteins; D008567:Membranes, Artificial; D010446:Peptide Fragments; D010713:Phosphatidylcholines; D010718:Phosphatidylserines; D010743:Phospholipids; D011510:Proteolipids; C484209:TMBIM6 protein, human; C020485:proteoliposomes; D019938:Cyclin D1; D002118:Calcium