A Glycophorin A-Like Framework for the Dimerization of Photosynthetic Core Complexes
A Glycophorin A-Like Framework for the Dimerization of Photosynthetic Core Complexes
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DOI：
10.1021/ja905903n
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发表时间：
2009-12-02
影响因子：
15
通讯作者：
Schulten, Klaus
中科院分区：
文献类型：
--
作者：
Hsin, Jen;Chipot, Christophe;Schulten, Klaus
光合细菌的核心复合物在光合作用中起着核心作用。该分子组装体由两种蛋白质复合物组成，即，光捕获复合物I（LH 1），其通过蛋白质结合的细菌叶绿素吸收太阳光，以及反应中心（RC），其使用LH复合物吸收的光激发能量来产生跨膜（TM）电荷梯度，随后用于能量转换。红细菌Rhodobacter（Rba.）在类球蛋白中，核心复合物还含有两个拷贝的单个TM α-螺旋蛋白PufX，并形成（RC-LH 1-PUfX）（2）二聚体。到目前为止，还没有高分辨率结构的报告，为整个核心复杂。特别地，Puff在（RC-LH 1-PufX）（2）二聚体中的位置仍然是许多争论的主题。在这里，一个建议的位置泡芙，需要其二聚化，检查。基于血型糖蛋白A（Glycophorin A，GpA）二聚体构建了Puff-二聚体模型，并通过一系列分子动力学（molecular dynamics，MID）模拟研究了该模型的稳健性。还确定了由于甘氨酸35被缬氨酸取代而引起的自由能变化，以评估该突变是否是不同Rba中不同Puff寡聚化状态的原因。物种目前的研究表明，泡芙螺旋形成一个稳定的GpA样二聚体的螺旋螺旋交叉角，可以构成高度弯曲和V形结构的Rba的报告的分子基础。球状体核心复合物二聚体。
The core complex in photosynthetic bacteria plays a central role in photosynthesis. This molecular assembly is composed of two protein complexes, viz., the light-harvesting complex I (LH1), which absorbs sunlight by means of the protein-bound bacteriochlorophylls, and the reaction center (RC), which uses the light-excitation energy absorbed by the LH complexes to produce a transmembrane (TM) charge gradient, subsequently employed for energy conversion. In Rhodobacter (Rba.) sphaeroides, the core complex contains, in addition, two copies of the single TM alpha-helix protein, PufX, and forms a (RC-LH1-PUfX)(2) dimer. To this date, no high-resotution structure has been reported for the entire core complex. In particular, the location of Puff within the (RC-LH1-PufX)(2) dimer is still the subject of much debate. Here, one of the proposed locations for Puff, requiring its dimerization, is examined. The Puff-dimer model on the basis of the glycophorin A (GpA) dimer was constructed, and its robustness was probed through a series of molecular dynamics (MID) simulations. The free-energy change due to the replacement of Gly35 by valine was also determined to assess whether this mutation is responsible for distinct Puff oligomerization states in different Rba. species. The present study shows that Puff helices form a stable GpA-like dimer with a helix-helix crossing angle that could constitute the molecular basis of the reported highly bent and V-shaped structure of the Rba. sphaeroides core complex dimer.