title: Palmitic and stearic acids bind Ca2+ with high affinity and form nonspecific channels in black-lipid membranes. Possible relation to Ca2+-activated mitochondrial pores.
abstract: A mitochondrial hydrophobic component that forms Ca2+-induced nonspecific ion channels in black-lipid membranes (Mironova et al., 1997) has been purified and its nature elucidated. It consists of long-chain saturated fatty acids--mainly palmitic and stearic. These fatty acids, similar to the mitochondrial hydrophobic component, bind Ca2+ with high affinity in comparison with unsaturated fatty acids, saturated fatty acids with shorter aliphatic chains, phospholipids, and other lipids. Ca2+-binding is inhibited by Mg2+ but not by K+. For palmitic acid, the Kd for Ca2+ was 5 microM at pH 8.5 and 15 microM at pH 7.5, with the Bmax of 0.48 +/- 0.08 mmol/g. This corresponds to one Ca2+ ion for eight palmitic acid molecules. The data of IR spectroscopy confirm that Ca2+ does not form ionic bonds with palmitic and stearic acids under hydrophobic conditions. It has been found that in the presence of Ca2+, palmitic and stearic acids, but not unsaturated FFA induce a nonspecific permeability in black-lipid membranes. Addition of Ca2+ in order to induce the permeability transition, increases the extractable amount of palmitic and stearic acids, the effect being prevented by a phospholipase A2 inhibitor. The possible involvement of palmitic and stearic acids in the mitochondrial nonspecific permeability is discussed.
authors.affiliation: Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region. mironova@venus.iteb.serpukhov.su
authors.forename: G D
authors.initials: GD
authors.lastname: Mironova
authors.forename: O
authors.initials: O
authors.lastname: Gateau-Roesch
authors.forename: C
authors.initials: C
authors.lastname: Levrat
authors.forename: E
authors.initials: E
authors.lastname: Gritsenko
authors.forename: E
authors.initials: E
authors.lastname: Pavlov
authors.forename: A V
authors.initials: AV
authors.lastname: Lazareva
authors.forename: E
authors.initials: E
authors.lastname: Limarenko
authors.forename: C
authors.initials: C
authors.lastname: Rey
authors.forename: P
authors.initials: P
authors.lastname: Louisot
authors.forename: N E
authors.initials: NE
authors.lastname: Saris
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D015220:Calcium Channels / Q000737:chemistry* / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D007476:Ionophores / Q000737:chemistry / Q000378:metabolism; D008567:Membranes, Artificial; D008930:Mitochondria, Liver / Q000187:drug effects / Q000648:ultrastructure; D019308:Palmitic Acid / Q000378:metabolism*; D010539:Permeability / Q000187:drug effects; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D051381:Rats; D013055:Spectrophotometry, Infrared; D013229:Stearic Acids / Q000378:metabolism*
chemical_list: D015220:Calcium Channels; D005227:Fatty Acids; D007476:Ionophores; D008567:Membranes, Artificial; D013229:Stearic Acids; D019308:Palmitic Acid; C031183:stearic acid; D010741:Phospholipases A; D054467:Phospholipases A2; D002118:Calcium