Acylation of monolysocardiolipin in rat heart

Abstract

Cardiolipin is a major mitochondrial membrane glycerophospholipid in the mammalian heart. In this study, the ability of the isolated intact rat heart to remodel cardiolipin and the mitochondrial enzyme activities that reacylate monolysocardiolipin to cardiolipin in vitro were characterized. Adult rat heart cardiolipin was found to contain primarily linoleic and oleic acids. Perfusion of the isolated intact rat heart in the Langendorff mode with various radioactive fatty acids, followed by analysis of radioactivity incorporated into cardiolipin and its immediate precursor phosphatidylglycerol, indicated that unsaturated fatty acids entered into cardiolipin mainly by deacylation followed by reacylation. The in vitro mitochondrial acylation of monolysocardiolipin to cardiolipin was coenzyme A-dependent with a pH optimum in the alkaline range. Significant activity was also present at physiological pH. With oleoyl-coenzyme A as substrate, the apparent Km for oleoyl-coenzyme A and monolysocardiolipin were 12.5 μm and 138.9 μm, respectively. With linoleoyl-coenzyme A as substrate, the apparent Km for linoleoyl-coenzyme A and monolysocardiolipin were 6.7 μm and 59.9 μm, respectively. Pre-incubation at 50°C resulted in different profiles of enzyme inactivation for the two activities. Both activities were affected similarly by phospholipids, triacsin C, and various lipid binding proteins but were affected differently by various detergents and myristoyl-coenzyme A. [3H]cardiolipin was not formed from monolyso[3H]cardiolipin in the absence of acyl-coenzyme A. Monolysocardiolipin acyltransferase activities were observed in mitochondria prepared from various other rat tissues. In summary, the data suggest that the isolated intact rat heart has the ability to rapidly remodel cardiolipin and that rat heart mitochondria contain coenzyme A-dependent acyl-transferase(s) for the acylation of monolysocardiolipin to cardiolipin. A simple and reproducible in vitro assay for the determination of acyl-coenzyme A-dependent monolysocardiolipin acyltransferase activity in mammalian tissues with exogenous monolysocardiolipin substrate is also presented.—Ma, B. J., W. A. Taylor, V. W. Dolinsky, and G. M. Hatch. Acylation of monolysocardiolipin in rat heart. J. Lipid Res. 1999. 40: 1837–1845. Cardiolipin is a major mitochondrial membrane glycerophospholipid in the mammalian heart. In this study, the ability of the isolated intact rat heart to remodel cardiolipin and the mitochondrial enzyme activities that reacylate monolysocardiolipin to cardiolipin in vitro were characterized. Adult rat heart cardiolipin was found to contain primarily linoleic and oleic acids. Perfusion of the isolated intact rat heart in the Langendorff mode with various radioactive fatty acids, followed by analysis of radioactivity incorporated into cardiolipin and its immediate precursor phosphatidylglycerol, indicated that unsaturated fatty acids entered into cardiolipin mainly by deacylation followed by reacylation. The in vitro mitochondrial acylation of monolysocardiolipin to cardiolipin was coenzyme A-dependent with a pH optimum in the alkaline range. Significant activity was also present at physiological pH. With oleoyl-coenzyme A as substrate, the apparent Km for oleoyl-coenzyme A and monolysocardiolipin were 12.5 μm and 138.9 μm, respectively. With linoleoyl-coenzyme A as substrate, the apparent Km for linoleoyl-coenzyme A and monolysocardiolipin were 6.7 μm and 59.9 μm, respectively. Pre-incubation at 50°C resulted in different profiles of enzyme inactivation for the two activities. Both activities were affected similarly by phospholipids, triacsin C, and various lipid binding proteins but were affected differently by various detergents and myristoyl-coenzyme A. [3H]cardiolipin was not formed from monolyso[3H]cardiolipin in the absence of acyl-coenzyme A. Monolysocardiolipin acyltransferase activities were observed in mitochondria prepared from various other rat tissues. In summary, the data suggest that the isolated intact rat heart has the ability to rapidly remodel cardiolipin and that rat heart mitochondria contain coenzyme A-dependent acyl-transferase(s) for the acylation of monolysocardiolipin to cardiolipin. A simple and reproducible in vitro assay for the determination of acyl-coenzyme A-dependent monolysocardiolipin acyltransferase activity in mammalian tissues with exogenous monolysocardiolipin substrate is also presented.—Ma, B. J., W. A. Taylor, V. W. Dolinsky, and G. M. Hatch. Acylation of monolysocardiolipin in rat heart. J. Lipid Res. 1999. 40: 1837–1845. Cardiolipin (CL), the first polyglycerophospholipid ever discovered, was initially isolated from beef heart by Mary Pangborn in 1942 (1Pangborn M. Isolation and purification of a serologically active phospholipid from beef heart.J. Biol. Chem. 1942; 143: 247-256Google Scholar). CL is a major membrane glycerophospholipid of mammalian mitochondria and, in the rat heart, CL comprises approximately 15% of the entire cardiac glycerophospholipid mass (for reviews see 2–5). CL is characteristically associated with the inner mitochondrial membrane where it may constitute as much as 21% of the total membrane glycerophospholipid mass of that organelle (6Stoffel W. Schiefer H-G. Biosynthesis and composition of phosphatides in outer and inner mitochondrial membranes.Hoppe-Seyler's Z. Physiol. Chem. 1968; 349: 1017-1026Google Scholar). In addition to its inner membrane localization some CL has been identified in the mitochondrial outer membrane (7Hovius R. Lambrechts H. Nicolay K. de Kruijff B. Improved methods to isolate and subfractionate rat liver mitochondria. Lipid composition of the inner and outer membrane.Biochim. Biophys. Acta. 1990; 1021: 217-226Google Scholar). CL was shown to be required for the reconstituted activity of a number of key mammalian mitochondrial enzymes involved in cellular energy metabolism including cytochrome c oxidase (8Vik S.B. Georgevich G. Capaldi R.A. Diphosphatidylglycerol is required for optimal activity of beef heart cytochrome c oxidase.Proc. Natl. Acad. Sci. USA. 1981; 78: 1456-1460Google Scholar), carnitine palmitoyltransferase (9Fiol C.J. Bieber L.L. Sigmoidal kinetics of purified beef heart mitochondrial carnitine palmitoyltransferase.J. Biol. Chem. 1984; 259: 13084-13088Google Scholar), creatine phosphokinase (10Muller M. Moser R. Cheneval D. Carafoli E. Cardiolipin is the membrane receptor for creatine phosphokinase.J. Biol. Chem. 1985; 260: 3839-3843Google Scholar), pyruvate translocator (11Hutson S.M. Roten S. Kaplan R.S. Solubilization and reconstitution of the branched-chain-alpha-keto acid transporter from rat heart mitochondria.Proc. Natl. Acad. Sci. USA. 1990; 87: 1028-1031Google Scholar), tricarboxylate carrier (12Kaplan R.S. Mayor J.A. Johnston N. Oliveira D.L. Purification and characterization of the reconstitutively active tricarboxylate transporter from rat liver mitochondria.J. Biol. Chem. 1990; 265: 13379-13385Google Scholar), mitochondrial glycerol-3-phosphate dehydrogenase (13Belezani Z.S. Janesik V. Role of cardiolipin in the functioning of the L-glycerol-3-phosphate dehydrogenase.Biochem. Biophys. Res. Commun. 1989; 159: 132-139Google Scholar), phosphate transporter (14Kadenbach B. Mende P. Kolbe H.V. Stipani I. Palmieri F. The mitochondrial phosphate carrier has an essential requirement for cardiolipin.FEBS Lett. 1982; 139: 109-112Google Scholar), ADP/ATP carrier (15Hoffman B. Stockl A. Schlame M. Beyer K. Klingenberg M. The reconstituted ADP/ATP carrier activity has an absolute requirement for cardiolipin as shown in cysteine mutants.J. Biol. Chem. 1994; 269: 1940-1944Google Scholar), and the ATP synthase (16Eble K.S. Coleman W.B. Hantgan R.R. Cunningham C.C. Tightly associated cardiolipin in bovine heart mitochondrial ATP synthase as analyzed by 31P nuclear magnetic resonance spectroscopy.J. Biol. Chem. 1990; 265: 19434-19440Google Scholar). CL interaction with the above proteins appeared to be specific as substitution with other mitochondrial phospholipids (for example, phosphatidylcholine and phosphatidylethanolamine) did not fully reconstitute activity (for review see 5). Under experimental conditions in which CL was removed, denaturation and complete loss in activity of many of these proteins was observed. Thus, the appropriate content of CL may be an important requirement for activation of enzymes involved in mitochondrial respiration. CL was shown to be synthesized via the cytidine-5′-diphosphate-1,2-diacyl-sn-glycerol (CDP-DG) pathway in the isolated rat heart (17Hatch G.M. Cardiolipin biosynthesis in the isolated heart.Biochem. J. 1994; 297: 201-208Google Scholar). In this pathway, phosphatidic acid (PA) was converted to CDP-DG. CDP-DG was then condensed with sn-glycerol-3-phosphate to phosphate which was rapidly converted to condensed with CDP-DG to CL fatty acid and the composition of CL appeared to be in the of fatty acids in the phosphatidylglycerol, and G. of Biophys. Acta. 1985; G.M. and in the heart and mammalian J. and Biophys. Acta. A. fatty acid composition of various tissues 1990; Scholar). The of CL was to be and the were shown to be by and of in M. S. cardiolipin in of and J. Scholar). The unsaturated linoleic appeared to be an important requirement for the binding of CL M. lipid and interaction in liver mitochondria by with to cardiolipin J. 1990; 265: Scholar). of the composition of CL was shown to the in cardiac mitochondria S. R. M. Cardiolipin in rat heart mitochondria to essential fatty 1990; S. R. M. from different bovine heart cytochrome c oxidase Scholar). In the activity of rat liver cytochrome c oxidase was reconstituted by the addition of The specific activity of the reconstituted cytochrome c oxidase and with different of Thus, in addition to CL the appropriate composition of CL may be for optimum mitochondrial The for the of was first by of The acylation of Biol. Chem. M. D. and Biophys. Acta. Scholar). The acyltransferase activities for mammalian phosphatidylcholine been (for review see was the that involved in the of acyl-coenzyme A-dependent of in rat liver was J. The of of by and mitochondria from rat Biol. Chem. Scholar). was not specific for linoleoyl-coenzyme A and was in rat liver mitochondria. a for the of CL in rat liver mitochondria was M. B. and in isolated rat liver J. 1990; Scholar). CL was to monolysocardiolipin and then with linoleoyl-coenzyme from to a deacylation followed by for CL as mitochondrial was shown to and exogenous CL H. of by mitochondrial Biophys. Acta. Cardiolipin by The activities of Biophys. Acta. M. P. purification and characterization of the from rat liver and localization of in the Lipid Res. Scholar). activities involved in the of to CL been identified in mammalian In this study, that the isolated intact rat heart has the ability to rapidly and remodel CL with unsaturated fatty acids. In the enzyme activities that to CL in rat heart mitochondrial this the first characterization of mitochondrial acyl-coenzyme A-dependent activity with exogenous present a simple and reproducible in vitro assay for the determination of this A of this was in G.M. of cardiolipin in rat Biol. Scholar). Adult were rat and in a and of to the of the heart fatty acid binding and were from and lipid binding were from of liver binding was from were from the and were from linoleoyl-coenzyme A and A were from linoleic acid and acyl-coenzyme were from of and by of bovine heart was from of the substrate was by as (17Hatch G.M. Cardiolipin biosynthesis in the isolated heart.Biochem. J. 1994; 297: 201-208Google Scholar). The fatty composition of the substrate was as The of in mammalian and was mainly of linoleic and oleic acids. was synthesized from CL as Cardiolipin by The activities of Biophys. Acta. Scholar). was from and were from N. and other were of and from fatty acid the was by and the heart was and via the a The in the was by the heart with prepared K. in Z. Physiol. Chem. a The heart was a and for was The of the heart the was via to the heart was for in the Langendorff mode with 12.5 of acid to bovine in a G.M. of of exogenous into cardiolipin not activation of the CDP-DG Biol. and of rat liver J. 1968; A and for the of of the of Scholar). In some the heart was with acid acid to bovine as The were and radioactivity incorporated into and CL was as assay of a rat heart mitochondrial mitochondria from other rat was prepared by the heart in pH followed by The was at for and the was at for The from this was in and then in of a A and the mitochondrial heart mitochondrial were for at in pH μm A μm A at pH μm A at pH μm in a of Under these optimum assay conditions the were to and at The substrate in was and in via in a for to addition to the assay The of the was at by The was by the addition of the radioactive acyl-coenzyme A substrate and by the addition of of of was The was and the was with of The was and in of A of the was a and CL was from other phospholipids in a acid was prepared as and addition of μm to the the of CL was of two loss of the the In some of CL from other was a The to CL was and in a and of incorporated into CL was approximately a activity was as radioactivity incorporated into CL in the of the substrate radioactivity incorporated into CL in the absence of the In some was in the assay In other mitochondrial were for with μm triacsin to In other μm rat heart rat liver were in the In other coenzyme and μm acid were in of A μm acid in of In acyl-coenzyme A μm of the acyl-coenzyme A was at a with the appropriate radioactive acyl-coenzyme A were in with and B. were at with were for with and the radioactive CL was isolated by as The radioactive CL was from the and with of for in pH at The formed was isolated by as and from the as The was to assay and the of was in the assay above acyl-coenzyme A. fatty acid and CL were from the as and fatty acid were prepared and analyzed as was as the isolated intact rat heart reacylate to initially the composition of CL and its immediate precursor in rat heart. in CL was of mainly and In was of mainly and oleic acids with of and linoleic acids. Thus, the composition of rat heart CL from its immediate phospholipid precursor then isolated rat in the Langendorff mode for with and acids to in a in of the isolated rat heart with fatty acids resulted in of these fatty acids into CL and The of radioactive unsaturated fatty acids into CL was approximately to the fatty acid In of radioactive unsaturated fatty acids into CL was In of radioactive acid into was much into fatty acids as acid into mainly by glycerophospholipid de B. and of acid in rat Biophys. Acta. Scholar), the data suggest that cardiac CL is to its appropriate composition in composition of rat heart cardiolipin and acid acid acid acid and were isolated from rat heart and the fatty acid composition was as in and of and as a of total fatty in a of and into rat heart cardiolipin and incorporated into Cardiolipin and acid acid acid were for in the Langendorff mode with acids and the radioactivity incorporated into CL and was as in and of in a CL and were isolated from rat heart and the fatty acid composition was as in and of and as a of total fatty were for in the Langendorff mode with acids and the radioactivity incorporated into CL and was as in and of activity not been in the heart. the ability of rat heart mitochondria to reacylate to CL in activities were in prepared isolated rat heart mitochondrial A and linoleoyl-coenzyme A were as the acyl-coenzyme A in this as these were the major found in rat heart The acylation of to CL was found to a pH optimum in the alkaline oleoyl-coenzyme A and linoleoyl-coenzyme A as oleoyl-coenzyme A was as substrate, the pH optimum for the was With linoleoyl-coenzyme A as substrate, the pH optimum for the was A loss of activity with was observed the pH was not with activity was observed at physiological pH. was to these in of was not observed. In the of ATP and coenzyme and mitochondrial some of was observed In in the of ATP and coenzyme and mitochondrial some of was observed was not formed acid acid was the was coenzyme A was as substrate, the of was of and was approximately of the activity observed with A as be converted to CL by was synthesized by of isolated from and to assay in the absence of acyl-coenzyme A. of was that activity not to the acylation of in the heart. A shown that fatty acid binding proteins the of oleoyl-coenzyme A into phosphatidic acid F. liver fatty acid binding with fatty USA. 1994; Scholar). The of rat liver rat heart did not the of from A from linoleoyl-coenzyme A the of did not the of from A from A not of and heart liver heart mitochondrial were in the absence of μm and activities were with A A as the of two and as a of With A as substrate, With A as substrate, The by in with μm in a heart mitochondrial were in the absence of μm and activities were with A A as the of two and as a of With A as substrate, With A as substrate, The by in with μm The apparent for oleoyl-coenzyme linoleoyl-coenzyme and were then The activities of the mitochondrial at different oleoyl-coenzyme A in the of a of were and the in a this the apparent Km of oleoyl-coenzyme A was to be 12.5 μm The activities of the mitochondrial at different in the of a of oleoyl-coenzyme A were then and the in a this the apparent Km of was to be 138.9 μm The activities of the mitochondrial at different linoleoyl-coenzyme A in the of a of were and the in a this the apparent Km of linoleoyl-coenzyme A was to be 6.7 μm The activities of the mitochondrial at different in the of a of linoleoyl-coenzyme A were then and the in a this the apparent Km of was to be 59.9 μm activities in rat heart mitochondria in the of various of linoleoyl-coenzyme A and activities were in rat heart mitochondrial in the of and various of A and the in a activities were in rat heart mitochondrial in the of μm A and various of and the in a the of two in The by the inactivation of the activities. heart mitochondrial were at for to and activity was activity was by at not Thus, the cardiac activities were conditions resulted in at 50°C resulted in a different of inactivation of the activities oleoyl-coenzyme A and linoleoyl-coenzyme A With linoleoyl-coenzyme A as substrate, for resulted in a in enzyme In with oleoyl-coenzyme A as substrate, for resulted in a in enzyme The above in enzyme inactivation the of activities for the acylation of to CL in rat heart mitochondria. the ability of various acyl-coenzyme to with from A A. The of a of acyl-coenzyme with A A in the assay the of the of myristoyl-coenzyme A of from oleoyl-coenzyme A but not from A. activity be affected by various detergents phospholipids the acyl-coenzyme A triacsin that to the acylation of with the acylation of with A was affected in the of various detergents at a of Both activities were affected similarly by the addition of and at a of In the of μm triacsin C, activities were not activities in various rat tissues. Significant activity was observed in the mitochondrial prepared from tissues The activities observed were for of the liver and with the the suggest that the isolated intact rat heart may rapidly and remodel CL and this the of a coenzyme A-dependent of acyl-coenzyme A heart mitochondrial were in the absence of various acyl-coenzyme and A A with the acyl-coenzyme A and activities were the of two and as a of With A as substrate, With A as substrate The by not in a of various detergents and phospholipids heart mitochondrial were in the absence of various detergents various phospholipids and activities were the of two and as a of The by With A as substrate, With A as substrate, in a activities in various were prepared from various tissues and activities were as in and the of two and as a of heart The by With A and heart activities were and respectively. in a heart mitochondrial were in the absence of various acyl-coenzyme and A A with the acyl-coenzyme A and activities were the of two and as a of With A as substrate, With A as substrate The by not heart mitochondrial were in the absence of various detergents various phospholipids and activities were the of two and as a of The by With A as substrate, With A as substrate, were prepared from various tissues and activities were as in and the of two and as a of heart The by With A and heart activities were and respectively. The of this were to the isolated intact rat heart the ability to remodel to a simple and reproducible in vitro assay for the of activity with exogenous substrate, and to the enzyme activities that to CL with physiological in rat heart mitochondrial of indicated that be to CL in the heart. of the isolated intact rat heart in the Langendorff mode with various fatty acids indicated that the of unsaturated fatty acids acid and oleic into CL was to that of a fatty acid which CL primarily via de in vitro acyl-coenzyme A-dependent activity was at physiological in isolated rat heart mitochondrial linoleoyl-coenzyme A oleoyl-coenzyme A as and these fatty acids the major found in rat heart was initially that the rat liver enzymes that CDP-DG for the de biosynthesis of CL some fatty substrate (for review see the of and were to that the rat liver enzymes of the CL pathway were not B. Schlame M. H. G. D. of phosphatidic and synthesized de in rat liver Biophys. Acta. 1989; Scholar). The rat liver CL synthase was shown to for various of CDP-DG P. H. the of cardiolipin and in rat liver of and the fatty acid composition of Biophys. Acta. Scholar). The fatty acid composition of the various phospholipid in the heart was shown to be a of including composition of (for review see A in indicated that acid was to and incorporated into phospholipids of including heart of the in the of for the acylation of rat liver mitochondrial Scholar). was not incorporated into which of CL in the rat heart. a in CL the of involved in the of CL that from that remodel other In the present study, the enzyme activities that reacylate to CL in rat heart mitochondria. The apparent Km observed for the oleoyl-coenzyme A and linoleoyl-coenzyme A initially suggest that these enzymes a for addition of these a is an of rat heart mitochondrial CL with and the in of acyl-coenzyme approximately μm R.S. acid in the and Scholar). The apparent Km for with linoleoyl-coenzyme A as substrate was approximately the apparent Km for with oleoyl-coenzyme A as the in of is approximately μm G. S. A. of and determination of phospholipids by analysis of H. G. content of and and with Scholar), it is that the of is for the the of linoleic oleic in these apparent Km the mitochondrial membrane in this may a of the activities of these enzymes to a purified enzyme reconstituted in and a has been observed in of of E. G. acid and phospholipid of different enzymes by a mammalian membrane as J. 1994; J. Role of fatty in the of metabolism and J. Scholar). as is found in in mitochondria G. S. A. of and determination of phospholipids by analysis of H. G. content of and and with Scholar), of of CL in a of in J. The of of by and mitochondria from rat Biol. Chem. Scholar). it be that the observed in apparent of the may be to in the of these the mitochondrial membrane indicated that and may with and the of acyl-coenzyme F. liver fatty acid binding with fatty USA. 1994; and for review see example, rat liver but not the of oleoyl-coenzyme A into phosphatidic acid F. liver fatty acid binding with fatty USA. 1994; Scholar). In study, addition of lipid binding proteins from did not enzyme data indicated that lipid binding proteins may not specific of the acyl-coenzyme A substrate to the linoleoyl-coenzyme A was as substrate, these lipid binding proteins appeared to enzyme is that lipid binding proteins as acyl-coenzyme A and it from into the mitochondria. with various phospholipid and triacsin addition indicated that with oleoyl-coenzyme A linoleoyl-coenzyme A were affected In the activities were different in the of various with oleoyl-coenzyme A linoleoyl-coenzyme A that the acylation of to CL may be by different In some were various acyl-coenzyme were in the the of myristoyl-coenzyme A activity oleoyl-coenzyme A was as substrate but not linoleoyl-coenzyme A was as may as Thus, be in of this data as enzymes in the of and addition the of the membrane and acyl-coenzyme A is an of and this is by D. at Scholar). The in inactivation profiles the two activities also for the of enzymes active involved in the acylation of to CL in rat heart mitochondria. was as substrate, radioactive CL was not observed. was in with a in isolated rat liver mitochondria M. B. and in isolated rat liver J. 1990; Scholar). Biosynthesis of the polyglycerophospholipid from by A followed by activity B. A. M. and in the of Scholar). The of acylation to in the absence of acyl-coenzyme A indicated that acylation by activity not to CL in rat heart mitochondria. In rat activity for the of CL was not observed M. B. and in isolated rat liver J. 1990; Scholar). mitochondria contain activity CL H. of by mitochondrial Biophys. Acta. M. P. purification and characterization of the from rat liver and localization of in the Lipid Res. and this activity M. B. and in isolated rat liver J. 1990; Scholar), it is that the formed in assay was by to the of The of CL in rat heart mitochondria the CL in as first by Schlame and M. B. and in isolated rat liver J. 1990; for rat liver mitochondrial A indicated that be to via a coenzyme A-dependent pathway in rat heart mitochondria P. V. G.M. The acylation of in rat for in vitro and in Biophys. Acta. Scholar). be that the radioactive CL formed from the oleoyl-coenzyme A linoleoyl-coenzyme A in the of the been to of the radioactive to CL via CL was as were shown to be of the purified rat liver CL synthase M. S. cardiolipin in of and J. Scholar). In in the absence of exogenous radioactive is formed in the of A P. V. G.M. The acylation of in rat for in vitro and in Biophys. Acta. Scholar). this was by the isolated rat heart of and into CL in the of into In of the and CL de into was much the of these into CL in (17Hatch G.M. Cardiolipin biosynthesis in the isolated heart.Biochem. J. 1994; 297: 201-208Google Scholar). was not as unsaturated fatty acids into mainly by deacylation followed by B. and of acid in rat Biophys. Acta. Scholar). The in the was a of and a the of the is to The assay not these two The acylation of to CL was observed in rat tissues in rat and that in the heart and the activity was observed in the two tissues heart and which active and not CL has been in cardiac G.M. G. of cardiolipin biosynthesis in cardiac by Biol. Chem. Scholar). of these with acid resulted in of the precursor into CL of in de CL In a in energy the of acid into CL was de CL biosynthesis was A. R. F. G. G.M. Cardiolipin in a in energy Scholar). of acid into CL was in G.M. G. Cardiolipin in with is to mitochondrial Biophys. Res. Commun. Scholar). The above and the that the in of mitochondrial CL is a and is of including and the of the for the of rat heart and for the of and for the of rat liver and for was by a from the of to G. M. H. is the of a and V. W. D. was the of a is a and of acyltransferase monolysocardiolipin acyltransferase cardiolipin monolysocardiolipin cytidine-5′-diphosphate-1,2-diacyl-sn-glycerol phosphatidic acid fatty acid binding lipid binding acyl-coenzyme A binding