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PufX 的 C 末端在聚光色素 1 复合物二聚体的形成和组装中起着关键作用,该复合物来自球形红杆菌。

The C-terminus of PufX plays a key role in dimerisation and assembly of the reaction center light-harvesting 1 complex from Rhodobacter sphaeroides.

机构信息

Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom.

Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom.

出版信息

Biochim Biophys Acta Bioenerg. 2017 Sep;1858(9):795-803. doi: 10.1016/j.bbabio.2017.06.001. Epub 2017 Jun 3.

Abstract

In bacterial photosynthesis reaction center-light-harvesting 1 (RC-LH1) complexes trap absorbed solar energy by generating a charge separated state. Subsequent electron and proton transfers form a quinol, destined to diffuse to the cytochrome bc complex. In bacteria such as Rhodobacter (Rba.) sphaeroides and Rba. capsulatus the PufX polypeptide creates a channel for quinone/quinol traffic across the LH1 complex that surrounds the RC, and it is therefore essential for photosynthetic growth. PufX also plays a key role in dimerization of the RC-LH1-PufX core complex, and the structure of the Rba. sphaeroides complex shows that the PufX C-terminus, particularly the region from X49-X53, likely mediates association of core monomers. To investigate this putative interaction we analysed mutations PufX R49L, PufX R53L, PufX R49/53L and PufX G52L by measuring photosynthetic growth, fractionation of detergent-solubilised membranes, formation of 2-D crystals and electron microscopy. We show that these mutations do not affect assembly of PufX within the core or photosynthetic growth but they do prevent dimerization, consistent with predictions from the RC-LH1-PufX structure. We obtained low resolution structures of monomeric core complexes with and without PufX, using electron microscopy of negatively stained single particles and 3D reconstruction; the monomeric complex with PufX corresponds to one half of the dimer structure whereas LH1 completely encloses the RC if the gene encoding PufX is deleted. On the basis of the insights gained from these mutagenesis and structural analyses we propose a sequence for assembly of the dimeric RC-LH1-PufX complex.

摘要

在细菌光合作用反应中心-捕光 1(RC-LH1)复合物中,通过生成电荷分离状态来捕获吸收的太阳能。随后的电子和质子转移形成醌,注定要扩散到细胞色素 bc 复合物。在 Rhodobacter(Rba.)sphaeroides 和 Rba. capsulatus 等细菌中,PufX 多肽为醌/氢醌在 LH1 复合物中穿过 RC 的通道创造了条件,因此对光合作用的生长至关重要。PufX 还在 RC-LH1-PufX 核心复合物的二聚化中发挥关键作用,并且 Rba. sphaeroides 复合物的结构表明,PufX C 端,特别是 X49-X53 区域,可能介导核心单体的结合。为了研究这种假定的相互作用,我们通过测量光合作用生长、去污剂溶解膜的分级分离、二维晶体形成和电子显微镜分析了 PufX R49L、PufX R53L、PufX R49/53L 和 PufX G52L 突变体。我们表明,这些突变不会影响 PufX 在核心内的组装或光合作用的生长,但它们确实阻止了二聚化,与 RC-LH1-PufX 结构的预测一致。我们使用负染色单颗粒的电子显微镜和 3D 重建获得了有和没有 PufX 的单体核心复合物的低分辨率结构;单体核心复合物与 PufX 对应于二聚体结构的一半,而如果删除编码 PufX 的基因,则 LH1 完全包围 RC。基于这些诱变和结构分析的见解,我们提出了二聚体 RC-LH1-PufX 复合物组装的序列。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/12a3/5538271/933853d8211b/gr1.jpg

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