BamA POTRA Domain Interacts with a Native Lipid Membrane Surface
BamA POTRA Domain Interacts with a Native Lipid Membrane Surface
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DOI：
10.1016/j.bpj.2016.05.010
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发表时间：
2016-06-21
影响因子：
3.4
通讯作者：
Im, Wonpil
中科院分区：
文献类型：
--
作者：
Fleming, Patrick J.;Patel, Dhilon S.;Im, Wonpil
革兰氏阴性细菌的外膜是一种不对称膜，外小叶上有脂多糖，周质小叶上有磷脂。这种外膜主要含有β-桶跨膜蛋白和脂化周质蛋白（脂蛋白）。多亚基蛋白β-桶装配机（BAM）催化β-桶蛋白插入和折叠到该膜中。在大肠杆菌中，BAM复合物由五个亚基组成，一个具有长周质结构域的核心跨膜β-桶（BamA）和四种脂蛋白（BamB/C/D/E）。BamA周质结构域由串联的五个球状亚结构域组成，称为POTRA基序，其是BAM复合物形成和与底物β-桶蛋白相互作用的关键。BAM复合物被认为经历构象循环，同时促进客户蛋白插入外膜。已经发表了描述周质POTRA结构域的可变构象和动力学的报告。因此，阐明全长BamA中POTRA结构域的构象动力学对于理解该分子复合物的功能是重要的。使用分子动力学模拟，我们提出的证据表明，POTRA结构域的构象灵活性调制的天然脂质膜的周质表面结合。此外，POTRA结构域的膜结合与BamB和BamD结合相容，表明不同POTRA结构域构象的构象选择可能参与BAM促进的外膜β-桶蛋白插入的机制。
The outer membrane of Gram-negative bacteria is an asymmetric membrane with lipopolysaccharides on the external leaflet and phospholipids on the periplasmic leaflet. This outer membrane contains mainly beta-barrel transmembrane proteins and lipidated periplasmic proteins (lipoproteins). The multisubunit protein beta-barrel assembly machine (BAM) catalyzes the insertion and folding of the beta-barrel proteins into this membrane. In Escherichia coli, the BAM complex consists of five subunits, a core transmembrane beta-barrel with a long periplasmic domain (BamA) and four lipoproteins (BamB/C/D/E). The BamA periplasmic domain is composed of five globular subdomains in tandem called POTRA motifs that are key to BAM complex formation and interaction with the substrate beta-barrel proteins. The BAM complex is believed to undergo conformational cycling while facilitating insertion of client proteins into the outer membrane. Reports describing variable conformations and dynamics of the periplasmic POTRA domain have been published. Therefore, elucidation of the conformational dynamics of the POTRA domain in full-length BamA is important to understand the function of this molecular complex. Using molecular dynamics simulations, we present evidence that the conformational flexibility of the POTRA domain is modulated by binding to the periplasmic surface of a native lipid membrane. Furthermore, membrane binding of the POTRA domain is compatible with both BamB and BamD binding, suggesting that conformational selection of different POTRA domain conformations may be involved in the mechanism of BAM-facilitated insertion of outer membrane beta-barrel proteins.