The physical state of lipid substrates provides transacylation specificity for tafazzin
作者:Michael Schlame、Devrim Acehan、Bob Berno、Yang Xu、Salvatore Valvo、Mindong Ren、David L Stokes、Richard M Epand
DOI:10.1038/nchembio.1064
日期:2012.10
Tafazzin, the mitochondrial transacylase that is deficient in Barth syndrome, selects lipid substrates in the inverted hexagonal phase but does not react with bilayer lipids. Cardiolipin is a mitochondrial phospholipid with a characteristic acyl chain composition that depends on the function of tafazzin, a phospholipid-lysophospholipid transacylase, although the enzyme itself lacks acyl specificity. We incubated isolated tafazzin with various mixtures of phospholipids and lysophospholipids, characterized the lipid phase by 31P-NMR and measured newly formed molecular species by MS. Substantial transacylation was observed only in nonbilayer lipid aggregates, and the substrate specificity was highly sensitive to the lipid phase. In particular, tetralinoleoyl-cardiolipin, a prototype molecular species, formed only under conditions that favor the inverted hexagonal phase. In isolated mitochondria, <1% of lipids participated in transacylations, suggesting that the action of tafazzin was limited to privileged lipid domains. We propose that tafazzin reacts with nonâbilayer-type lipid domains that occur in curved or hemifused membrane zones and that acyl specificity is driven by the packing properties of these domains.
Tafazzin是线粒体转酰基酶,在巴特综合征中缺乏,它在倒六边形相中选择脂质底物,但不会与双层脂质发生反应。 心磷脂是一种线粒体磷脂,具有独特的酰基链组成,这种组成取决于tafazzin的功能,而tafazzin是一种磷脂-溶血磷脂转酰基酶,尽管酶本身缺乏酰基特异性。我们将分离的tafazzin与各种磷脂和溶血磷脂混合物一起培养,通过31P-NMR表征脂质相,并通过MS测量新形成的分子种类。仅在非双层脂质聚集物中观察到大量的转酰基化,底物特异性对脂质相高度敏感。特别是,四亚油酰基-心磷脂是一种原型分子种类,仅在有利于倒六边形相的条件下形成。在分离的线粒体中,只有不到1%的脂质参与转酰基化,这表明tafazzin的作用仅限于特权脂质域。我们提出,tafazzin与弯曲或半融合膜区域中的非双层型脂质域发生反应,而酰基特异性是由这些域的堆积特性驱动的。