Nishiyama Ken-ichi, Shimamoto Keiko
Biomol Concepts. 2014 Oct;5(5):429-38. doi: 10.1515/bmc-2014-0030.
A novel factor for membrane protein integration, from the cytoplasmic membrane of Escherichia coli, named MPIase (membrane protein integrase), has recently been identified and characterized. MPIase was revealed to be essential for the membrane integration of a subset of membrane proteins, despite that such integration reactions have been, thus far, thought to occur spontaneously. The structure determination study revealed that MPIase is a novel glycolipid comprising a glycan chain with three N-acetylated amino sugars connected to diacylglycerol through a pyrophosphate linker. As MPIase catalyzes membrane protein integration, we propose that MPIase is a glycolipozyme on the basis of its enzyme-like function. The glycan chain exhibits a molecular chaperone-like function by directly interacting with substrate membrane proteins. Moreover, MPIase also affects the dimer structure of SecYEG, a translocon, thereby significantly stimulating preprotein translocation. The molecular mechanisms of MPIase functions will be outlined.
最近，一种来自大肠杆菌细胞质膜的新型膜蛋白整合因子被鉴定并表征，命名为MPIase（膜蛋白整合酶）。尽管迄今为止认为此类整合反应是自发发生的，但MPIase被证明对于一部分膜蛋白的膜整合至关重要。结构测定研究表明，MPIase是一种新型糖脂，由一条带有三个N-乙酰化氨基糖的聚糖链通过焦磷酸连接子连接到二酰基甘油组成。由于MPIase催化膜蛋白整合，基于其类似酶的功能，我们提出MPIase是一种糖脂酶。聚糖链通过直接与底物膜蛋白相互作用发挥分子伴侣样功能。此外，MPIase还影响转运体SecYEG的二聚体结构，从而显著刺激前体蛋白转运。将概述MPIase功能的分子机制。
