Membrane mimetic environments alter the conformation of the outer membrane protein BtuB
Membrane mimetic environments alter the conformation of the outer membrane protein BtuB
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DOI：
10.1021/ja0376442
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发表时间：
2003-11-19
影响因子：
15
通讯作者：
Cafiso, DS
中科院分区：
文献类型：
--
作者：
Fanucci, GE;Lee, JY;Cafiso, DS
由洗涤剂或短链磷脂形成的模拟膜环境广泛应用于膜蛋白的结构研究。利用位点定向自旋标记（SDSL），我们发现胶束和各向同性的双细胞环境改变了BtuB的n端区域，BtuB是在大肠杆菌中发现的外膜维生素b12转运体。这些膜模拟系统促进蛋白质的n端展开，而这在蛋白质处于天然或重组双分子层时是不会发生的。BtuB的n端Ton盒已被证明以两种构象存在，这取决于底物的存在或不存在。然而，洗涤剂不稳定构象不同于无底物或底物结合形式的这种转运体。这个例子表明，膜模拟系统并不总是取代生物膜提供的层状双层环境。
Membrane mimetic environments formed from detergents or short-chain phospholipids are widely utilized in structural studies of membrane proteins. Using site-directed spin labeling (SDSL), we show that micelle and isotropic bicellar environments alter the N-terminal region of BtuB, the outer membrane vitamin B12transporter found inEscherichia coli. These membrane mimetic systems promote an unfolding of the N-terminus of the protein that does not occur when the protein is in either native or reconstituted bilayers. The N-terminal Ton box of BtuB has been shown to exist in two conformations, depending upon the presence or absence of substrate. However, the detergent-destabilized conformation is different from either the substrate-free or the substrate-bound form of this transporter. This example demonstrates that membrane mimetic systems will not always substitute for the lamellar bilayer environment provided by a biological membrane.