Tani Motohiro, Kuge Osamu
Department of Chemistry, Faculty of Sciences, Kyushu University, 6-10-1, Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
Biochem Biophys Res Commun. 2009 Apr 10;381(3):328-32. doi: 10.1016/j.bbrc.2009.02.063. Epub 2009 Feb 20.
Sphingomyelin synthase (SMS) is an enzyme that catalyzes the transfer of phosphocholine from phosphatidylcholine to ceramide for sphingomyelin synthesis. Here, we show that SMS2 is palmitoylated at cysteine residues via thioester bonds in the COOH-terminal cytoplasmic tail. [3H]palmitic acid labeling of SMS1 or SMS2-overexpressing HEK293 cells revealed that SMS2, but not SMS1, is palmitoylated. Site-directed mutagenesis of cysteine residues to alanine ones indicated that the COOH-terminal cysteine cluster of the enzyme is palmitoylated. Mutation of all potential palmitoylation sites resulted in a dramatic reduction in the plasma membrane distribution of SMS2, whereas it did not affect the in vitro enzyme activity. These results suggested that this posttranslational modification is important for determination of the subcellular localization of SMS2.
鞘磷脂合酶（SMS）是一种催化磷脂酰胆碱的磷酸胆碱转移至神经酰胺以合成鞘磷脂的酶。在此，我们发现SMS2在COOH末端胞质尾区通过硫酯键在半胱氨酸残基处发生棕榈酰化。对过表达SMS1或SMS2的HEK293细胞进行[3H]棕榈酸标记显示，被棕榈酰化的是SMS2而非SMS1。将半胱氨酸残基定点突变为丙氨酸表明该酶的COOH末端半胱氨酸簇被棕榈酰化。所有潜在棕榈酰化位点的突变导致SMS2在质膜的分布显著减少，而这并不影响其体外酶活性。这些结果表明这种翻译后修饰对于确定SMS2的亚细胞定位很重要。
