The Acyl-Acyl Carrier Protein Synthetase from Synechocystis sp PCC 6803 Mediates Fatty Acid Import
The Acyl-Acyl Carrier Protein Synthetase from Synechocystis sp PCC 6803 Mediates Fatty Acid Import
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DOI：
10.1104/pp.112.195263
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发表时间：
2012-06-01
期刊：
影响因子：
7.4
通讯作者：
Gierth, Markus
中科院分区：
文献类型：
--
作者：
von Berlepsch, Simon;Kunz, Hans-Henning;Gierth, Markus
脂肪酸跨生物膜的转移是一个很大程度上未表征的过程，尽管它在几种高等植物细胞器如叶绿体、过氧化物酶体或内质网的膜上是必不可少的。在这里，我们分析了单细胞蓝藻集胞藻属PCC 6803作为一个模型系统，以规避冗余的问题，在真核生物中遇到的功能丧失突变体。细胞缺乏唯一的细胞质集胞藻酰基-酰基载体蛋白合成酶（SynAas）是高度耐外部提供的α-亚麻酸，而野生型细胞漂白后，这种治疗。漂白野生型细胞伴随着α-亚麻酸的总脂质的持续增加，而没有这样的积累可以观察到SynAas缺陷细胞（三角洲synaas）。当SynAas在生育酚缺乏，α-亚麻酸过敏集胞藻突变体Delta slr 1736中被破坏时，双突变细胞显示出与Delta synaas相同的抗性表型。此外，异源表达的SynAas在酵母（酿酒酵母）突变体缺乏主要的酵母脂肪酸输入蛋白Fat 1 p（德尔塔fat 1）导致恢复野生型对外源α-亚麻酸的敏感性，否则耐德尔塔fat 1突变体，表明SynAas是功能等同于Fat 1 p。此外，脂质体测定提供了纯化的SynAas蛋白通过合成[C-14]亚麻酰-酰基载体蛋白介导α-[C-14]亚麻酸从预装脂质体膜中回收的能力的直接证据。总之，我们的数据表明，酰基活化酶如SynAas是必要的，足以介导脂肪酸转移穿过生物膜。
The transfer of fatty acids across biological membranes is a largely uncharacterized process, although it is essential at membranes of several higher plant organelles like chloroplasts, peroxisomes, or the endoplasmic reticulum. Here, we analyzed loss-of-function mutants of the unicellular cyanobacterium Synechocystis sp. PCC 6803 as a model system to circumvent redundancy problems encountered in eukaryotic organisms. Cells deficient in the only cytoplasmic Synechocystis acyl-acyl carrier protein synthetase (SynAas) were highly resistant to externally provided alpha-linolenic acid, whereas wild-type cells bleached upon this treatment. Bleaching of wild-type cells was accompanied by a continuous increase of alpha-linolenic acid in total lipids, whereas no such accumulation could be observed in SynAas-deficient cells (Delta synaas). When SynAas was disrupted in the tocopherol-deficient, alpha-linolenic acid-hypersensitive Synechocystis mutant Delta slr1736, double mutant cells displayed the same resistance phenotype as Delta synaas. Moreover, heterologous expression of SynAas in yeast (Saccharomyces cerevisiae) mutants lacking the major yeast fatty acid import protein Fat1p (Delta fat1) led to the restoration of wild-type sensitivity against exogenous alpha-linolenic acid of the otherwise resistant Delta fat1 mutant, indicating that SynAas is functionally equivalent to Fat1p. In addition, liposome assays provided direct evidence for the ability of purified SynAas protein to mediate alpha-[C-14] linolenic acid retrieval from preloaded liposome membranes via the synthesis of [C-14] linolenoyl-acyl carrier protein. Taken together, our data show that an acyl-activating enzyme like SynAas is necessary and sufficient to mediate the transfer of fatty acids across a biological membrane.