The PuhB protein of Rhodobacter capsulatus functions in photosynthetic reaction center assembly with a secondary effect on light-harvesting complex 1
The PuhB protein of Rhodobacter capsulatus functions in photosynthetic reaction center assembly with a secondary effect on light-harvesting complex 1
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DOI：
10.1128/jb.187.4.1334-1343.2005
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发表时间：
2005-02-01
影响因子：
3.2
通讯作者：
Beatty, JT
中科院分区：
文献类型：
--
作者：
Aklujkar, M;Prince, RC;Beatty, JT
紫色光合细菌如荚膜红细菌的光合机构的核心由与捕光复合物1（LH 1）和PufX多肽密切相关的反应中心（RC）组成。RC和LH 1组分的丰度先前显示取决于puhB基因（以前称为orf 214）的产物。我们在这里报告说，破坏puhB减少RC组装，与LH 1组装的间接影响，并减少PufX的量。在半需氧生长条件下，核心复合物是目前在puhB突变体的水平降低。在将半需氧培养物转移到光合（厌氧光照）条件下后，RC/LH 1复合物仅变得稍微丰富，并且PufX的量随着细胞开始光合生长而增加。我们发现，puhB干扰菌株的光合生长，R。capsulatus在长时间的滞后期后开始，这是由于生理适应而不是二次突变。使用杂交蛋白表达系统，我们确定了三个预测的跨膜段的PuhB能够跨越细胞膜和第二个跨膜段可以介导的PuhB的自我关联。我们讨论了PuhB作为二聚体RC组装因子的可能功能。
The core of the photosynthetic apparatus of purple photosynthetic bacteria such as Rhodobacter capsulatus consists of a reaction center (RC) intimately associated with light-harvesting complex 1 (LH1) and the PufX polypeptide. The abundance of the RC and LH1 components was previously shown to depend on the product of the puhB gene (formerly known as orf214). We report here that disruption of puhB diminishes RC assembly, with an indirect effect on LH1 assembly, and reduces the amount of PufX. Under semiaerobic growth conditions, the core complex was present at a reduced level in puhB mutants. After transfer of semiaerobically grown cultures to photosynthetic (anaerobic illuminated) conditions, the RC/LH1 complex became only slightly more abundant, and the amount of PufX increased as cells began photosynthetic growth. We discovered that the photosynthetic growth of puhB disruption strains of R. capsulatus starts after a long lag period, which is due to physiological adaptation rather than secondary mutations. Using a hybrid protein expression system, we determined that the three predicted transmembrane segments of PuhB are capable of spanning a cell membrane and that the second transmembrane segment could mediate self-association of PuhB. We discuss the possible function of PuhB as a dimeric RC assembly factor.