Topology of phosphatidylserine synthase 1 in the endoplasmic reticulum membrane
Topology of phosphatidylserine synthase 1 in the endoplasmic reticulum membrane
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DOI：
10.1002/pro.4182
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发表时间：
2021-09-22
期刊：
影响因子：
8
通讯作者：
Kuge, Osamu
中科院分区：
文献类型：
--
作者：
Miyata, Non;Kuge, Osamu
哺乳动物细胞的磷脂酰丝氨酸(PS)合成酶1(PSS1)是内质网(ER)的一种跨膜蛋白，受PS产物的抑制调节。丙氨酸扫描突变PSS1发现了8个氨基酸残基对其活性至关重要，6个氨基酸残基对其调控至关重要。此外，已鉴定出人类PSS1基因的三个错义突变，它们导致PSS1的调节功能障碍，并导致Lenz-Majewski综合征。在本研究中，我们通过表位插入和免疫荧光的方法研究了PSS1的膜拓扑结构。根据PSS1的拓扑分析支持的10跨膜片段模型，所有与酶活性有关的8个氨基酸残基都定位在内质网脂双层的管腔侧，而参与酶调控的9个氨基酸残基都定位在内质网脂双层的胞浆或胞质侧。这种功能氨基酸残基的定位表明，PSS1在内质膜的细胞质小叶上受到PS抑制的调节，并在管腔小叶合成PS。
Phosphatidylserine (PS) synthase 1 (PSS1) of mammalian cells is a multiple membrane-spanning protein of the endoplasmic reticulum (ER) and regulated by inhibition with the product PS. Alanine-scanning mutagenesis of PSS1 has revealed eight amino acid residues as those crucial for its activity and six as those important for its regulation. Furthermore, three missense mutations in the human PSS1 gene, which lead to regulatory dysfunctions of PSS1 and are causative of Lenz-Majewski syndrome, have been identified. In this study, we investigated the membrane topology of PSS1 by means of epitope insertion and immunofluorescence. According to a 10-transmembrane segment model supported by topology analysis of PSS1, all the 8 amino acid residues crucial for the enzyme activity were localized to the luminal side of the lipid bilayer or the lumen of the ER, whereas all the 9 amino acid residues involved in the enzyme regulation were localized to the cytosol or the cytoplasmic side of the lipid bilayer of the ER. This localization of the functional amino acid residues suggests that PSS1 is regulated by inhibition with PS in the cytoplasmic leaflet of the ER membrane and synthesizes PS at the luminal leaflet.