Substrate Specificity and Membrane Topology of Escherichia coli PgpB, an Undecaprenyl Pyrophosphate Phosphatase*
Substrate Specificity and Membrane Topology of Escherichia coli PgpB, an Undecaprenyl Pyrophosphate Phosphatase*
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DOI：
10.1074/jbc.m800394200
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发表时间：
2008-06
影响因子：
4.8
通讯作者：
T. Touzé;D. Blanot;D. Mengin-Lecreulx
中科院分区：
文献类型：
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作者：
T. Touzé;D. Blanot;D. Mengin-Lecreulx
脂质载体磷酸十一异戊烯酯（C55-P）的合成需要其前体焦磷酸十一异戊烯酯（C55-PP）的去磷酸化。后一种脂质在细胞质中重新合成，并且在从周质中的C55-PP连接的聚糖释放后也再生。在大肠杆菌中，C55-PP的去磷酸化被证明涉及四个完整的膜蛋白，巴卡，和2型磷脂酸磷酸酶家族的三个成员，PgpB，YbjG和YeiU。在此，PgpB蛋白被纯化至均一，并检测其磷酸酶活性。该酶被证明催化C55-PP的去磷酸化，与焦磷酸二酰甘油和焦磷酸法呢酯（C15-PP）脂质底物相比，效率相对较低。然而，在体外C55-PP磷酸酶活性的PgpB特异性增强不同的磷脂。我们假设磷脂是重要的决定因素，以确保适当的构象的非典型长轴C55载体脂质膜。此外，拓扑分析表明，PgpB包含六个跨膜段，一个大的周质环，和2型磷脂酸磷酸酶签名残基在周质位置。
The synthesis of the lipid carrier undecaprenyl phosphate (C55-P) requires the dephosphorylation of its precursor, undecaprenyl pyrophosphate (C55-PP). The latter lipid is synthesized de novo in the cytosol and is also regenerated after its release from the C55-PP-linked glycans in the periplasm. In Escherichia coli the dephosphorylation of C55-PP was shown to involve four integral membrane proteins, BacA, and three members of the type 2 phosphatidic acid phosphatase family, PgpB, YbjG, and YeiU. Here, the PgpB protein was purified to homogeneity, and its phosphatase activity was examined. This enzyme was shown to catalyze the dephosphorylation of C55-PP with a relatively low efficiency compared with diacylglycerol pyrophosphate and farnesyl pyrophosphate (C15-PP) lipid substrates. However, the in vitro C55-PP phosphatase activity of PgpB was specifically enhanced by different phospholipids. We hypothesize that the phospholipids are important determinants to ensure proper conformation of the atypical long axis C55 carrier lipid in membranes. Furthermore, a topological analysis demonstrated that PgpB contains six transmembrane segments, a large periplasmic loop, and the type 2 phosphatidic acid phosphatase signature residues at a periplasmic location.