In meso structure of the cobalamin transporter, BtuB, at 1.95 Å resolution
In meso structure of the cobalamin transporter, BtuB, at 1.95 Å resolution
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DOI：
10.1016/j.jmb.2006.09.022
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发表时间：
2006-12-08
影响因子：
5.6
通讯作者：
Caffrey, M.
中科院分区：
文献类型：
--
作者：
Cherezov, V.;Yamashita, E.;Caffrey, M.
维生素B-12和结肠素受体BtuB的载脂蛋白形式的晶体已经用基于膜的介观技术生长出来，其衍射率为1.95埃。这种蛋白质的结构在几个细节上与通过更传统的、以洗涤剂为基础的(在Surfo中)方法培养的蛋白质的结构不同。这些差异中的一些包括(I)五个N-末端残基在中空区域中被分解，(Ii)在孵化区域中的残基57-62和环21-22中的残基574-581在中空区域中无序并在表面上有序，(Iii)环7-8中的残基278-287在中空区域中被分解，(Iv)环9-10中的残基324-331，环13-14中的396-411，环15-16中的442-458和环19-20中的526-541在两种晶型之间具有很大的位置差异，正如在孵化区域中的残基86-96一样，以及(V)吨盒中残基6和7的构象(被认为对信号转导和底物运输至关重要)在两种结构中完全不同。重要的是，残基6和7的介观取向类似于维生素B-12带电状态。这些数据表明，文献中报道的残基6和7的“底物诱导”180度旋转可能不是一个独特的信号事件。评估了这些发现与从定点定向自旋标记和电子顺磁共振测量中收集的结构、动力学和功能洞察相吻合的程度。在中温生长的晶体中堆积是致密的和分层的，这与目前脂类中间相中膜蛋白的结晶形成模型一致。分层堆积被用来定位蛋白质的跨膜疏水表面。一般来说，这与蛋白质中色氨酸、酪氨酸、脂质和C-αB因子的分布以及基于转移自由能计算的预测是一致的。(C)2006爱思唯尔有限公司。保留所有权利。
Crystals of the apo form of the vitamin B-12 and colicin receptor, BtuB, that diffract to 1.95 angstrom have been grown by the membrane-based in meso technique. The structure of the protein differs in several details from that of its counterpart grown by the more traditional, detergent-based (in surfo) method. Some of these differences include (i) the five N-terminal residues are resolved in meso, (ii) residues 57-62 in the hatch domain and residues 574-581 in loop 21-22 are disordered in meso and are ordered in surfo, (iii) residues 278-287 in loop 7-8 are resolved in meso, (iv) residues 324-331 in loop 9-10, 396-411 in loop 13-14, 442-458 in loop 15-16 and 526-541 in loop 19-20 have large differences in position between the two crystal forms, as have residues 86-96 in the hatch domain, and (v) the conformation of residues 6 and 7 in the Ton box (considered critical to signal transduction and substrate transport) are entirely different in the two structures. Importantly, the in meso orientation of residues 6 and 7 is similar to that of the vitamin B-12-charged state. These data suggest that the "substrateinduced" 180 degrees-rotation of residues 6 and 7 reported in the literature may not be a unique signalling event. The extent to which these findings agree with structural, dynamic and functional insights gleaned from site-directed spin labelling and electron paramagnetic resonance measurements is evaluated. Packing in in meso grown crystals is dense and layered, consistent with the current model for crystallogenesis of membrane proteins in lipidic mesophases. Layered packing has been used to locate the transmembrane hydrophobic surface of the protein. Generally, this is consistent with tryptophan, tyrosine, lipid and C-alpha B-factor distributions in the protein, and with predictions based on transfer free energy calculations. (c) 2006 Elsevier Ltd. All rights reserved.