Grilley M M, Stock S D, Dickson R C, Lester R L, Takemoto J Y
Department of Biology, Utah State University, Logan, Utah 84322, USA.
J Biol Chem. 1998 May 1;273(18):11062-8. doi: 10.1074/jbc.273.18.11062.
The Saccharomyces cerevisiae gene SYR2, necessary for growth inhibition by the cyclic lipodepsipeptide syringomycin E, is shown to be required for 4-hydroxylation of long chain bases in sphingolipid biosynthesis. Four lines of support for this conclusion are presented: (a) the predicted Syr2p shows sequence similarity to diiron-binding membrane enzymes involved in oxygen-dependent modifications of hydrocarbon substrates, (b) yeast strains carrying a disrupted SYR2 allele produced sphingoid long chain bases lacking the 4-hydroxyl group present in wild type strains, (c) 4-hydroxylase activity was increased in microsomes prepared from a SYR2 overexpression strain, and (d) the syringomycin E resistance phenotype of a syr2 mutant strain was suppressed when grown under conditions in which exogenous 4-hydroxysphingoid long chain bases were incorporated into sphingolipids. The syr2 strain produced wild type levels of sphingolipids, substantial levels of hydroxylated very long chain fatty acids, and the full complement of normal yeast sphingolipid head groups. These results show that the SYR2 gene is required for the 4-hydroxylation reaction of sphingolipid long chain bases, that this hydroxylation is not essential for growth, and that the 4-hydroxyl group of sphingolipids is necessary for syringomycin E action on yeast.
酿酒酵母基因SYR2是环状脂肽类抗生素丁香霉素E抑制生长所必需的，研究表明它在鞘脂生物合成中长链碱基的4-羟基化过程中发挥作用。支持这一结论的证据有四点：（a）预测的Syr2p与参与烃类底物氧依赖性修饰的双铁结合膜酶具有序列相似性；（b）携带SYR2等位基因破坏的酵母菌株产生的鞘氨醇长链碱基缺乏野生型菌株中存在的4-羟基；（c）从SYR2过表达菌株制备的微粒体中4-羟化酶活性增加；（d）当在将外源4-羟基鞘氨醇长链碱基掺入鞘脂的条件下生长时，syr2突变菌株的丁香霉素E抗性表型受到抑制。syr2菌株产生野生型水平的鞘脂、大量的羟基化超长链脂肪酸以及正常酵母鞘脂头部基团的完整组成。这些结果表明，SYR2基因是鞘脂长链碱基4-羟基化反应所必需的，这种羟基化对生长并非必不可少，并且鞘脂的4-羟基对于丁香霉素E对酵母的作用是必需的。
