THE CYANOBACTERIAL CHLOROPHYLL‐BINDING‐PROTEIN ISIA ACTS TO INCREASE THE IN VIVO EFFECTIVE ABSORPTION CROSS‐SECTION OF PSI UNDER IRON LIMITATION 1
THE CYANOBACTERIAL CHLOROPHYLL‐BINDING‐PROTEIN ISIA ACTS TO INCREASE THE IN VIVO EFFECTIVE ABSORPTION CROSS‐SECTION OF PSI UNDER IRON LIMITATION 1
复制标题
DOI：
10.1111/j.1529-8817.2011.01092.x
复制
发表时间：
2012-02
影响因子：
2.9
通讯作者：
T. Ryan-Keogh;A. Macey;A. Cockshutt;C. M. Moore;T. Bibby
中科院分区：
文献类型：
--
作者：
T. Ryan-Keogh;A. Macey;A. Cockshutt;C. M. Moore;T. Bibby
铁的可利用性限制了世界上30%以上海洋的初级生产;因此浮游植物已经发展出适应策略。特别是，蓝细菌在铁胁迫下表达IsiA（铁胁迫诱导），它可以成为细胞中最丰富的chl结合蛋白。在铁有限的海洋区域与显着的蓝藻生物量，IsiA可能代表总叶绿素的一个重要部分。我们在体内光谱测量了光合反应中心PSI的有效截面（σ PSI），并在模型蓝藻集胞藻PCC 6803中生化定量了PSI，PSII和IsiA的绝对丰度。我们证明了IsiA的积累导致σ PSI增加约60%，与基于来自蓝藻的生化分离的IsiA-PSI超复合物的结构的横截面的理论增加一致。通过推导叶绿素预算，我们认为IsiA作为PSI的光捕获天线发挥着主要作用。在培养物中进行性铁应激时，IsiA继续积累，而σ PSI没有随之增加，这表明IsiA可能具有次要作用。在自然种群中，IsiA的未偶联池的潜在生理意义仍有待确定。然而，作为PSI天线的功能作用表明大部分IsiA结合的chl直接参与光合电子传递。
Iron availability limits primary production in >30% of the world’s oceans; hence phytoplankton have developed acclimation strategies. In particular, cyanobacteria express IsiA (iron‐stress‐induced) under iron stress, which can become the most abundant chl‐binding protein in the cell. Within iron‐limited oceanic regions with significant cyanobacterial biomass, IsiA may represent a significant fraction of the total chl. We spectroscopically measured the effective cross‐section of the photosynthetic reaction center PSI (σPSI) in vivo and biochemically quantified the absolute abundance of PSI, PSII, and IsiA in the model cyanobacterium Synechocystis sp. PCC 6803. We demonstrate that accumulation of IsiA results in a ∼60% increase in σPSI, in agreement with the theoretical increase in cross‐section based on the structure of the biochemically isolated IsiA‐PSI supercomplex from cyanobacteria. Deriving a chl budget, we suggest that IsiA plays a primary role as a light‐harvesting antenna for PSI. On progressive iron‐stress in culture, IsiA continues to accumulate without a concomitant increase in σPSI, suggesting that there may be a secondary role for IsiA. In natural populations, the potential physiological significance of the uncoupled pool of IsiA remains to be established. However, the functional role as a PSI antenna suggests that a large fraction of IsiA‐bound chl is directly involved in photosynthetic electron transport.