Functional diversification of two bilin reductases for light perception and harvesting in unique cyanobacterium Acaryochloris marina MBIC 11017
Functional diversification of two bilin reductases for light perception and harvesting in unique cyanobacterium Acaryochloris marina MBIC 11017
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DOI：
10.1111/febs.15230
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发表时间：
2020-02-15
期刊：
影响因子：
5.4
通讯作者：
Narikawa, Rei
中科院分区：
文献类型：
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作者：
Miyake, Keita;Fushimi, Keiji;Narikawa, Rei
Bilin 色素分别通过与蓝细菌色素 (CBCR) 和藻胆体 (PBS) 结合，在蓝细菌的光感知和收获中发挥重要作用。在各种蓝细菌中，Acaryocholis marina MBIC 11017 (A. marina 11017) 例外地使用叶绿素 d 作为主要光合色素，比典型色素叶绿素 a 吸收更长波长的光，这表明存在比其他蓝藻感知更长波长光的系统。另一方面，A. marina 11017 具有 PBS 装置来收集短波长橙色光，类似于大多数蓝细菌。因此，A. marina 11017 可能会通过使用胆色素来感知较长波长的光并收获较短波长的光。藻蓝蛋白（PCB）是这两个系统的主要胆色素。藻蓝蛋白：铁氧还蛋白氧化还原酶 (PcyA) 通过中间体 18(1),18(2)-二氢胆绿素 (18(1),18(2)-DHBV) 催化胆绿素合成 PCB，导致吸收波长逐步缩短。在这项研究中，我们发现 A. marina 11017 异常编码两个 PcyA 同源物，AmPcyAc 和 AmPcyAp。 AmPcyAc 在主染色体上编码，具有大多数光感受器基因，而 AmPcyAp 在质粒上编码，具有 PBS 相关基因。在 AmPcyAc 催化反应期间观察到 18(1),18(2)-DHBV 长时间大量积累，而在 AmPcyAp 催化反应期间 18(1),18(2)-DHBV 在短时间内短暂积累。 CBCR可以通过18(1),18(2)-DHBV的掺入来感知更长波长的远红光，而PBS只能通过PCB的掺入来收获橙光，这表明PcyA的功能多样化为AmPcyAc和AmPcyAp，分别为光感知和收获系统提供18(1),18(2)-DHBV和PCB。
Bilin pigments play important roles for both light perception and harvesting in cyanobacteria by binding to cyanobacteriochromes (CBCRs) and phycobilisomes (PBS), respectively. Among various cyanobacteria, Acaryochloris marina MBIC 11017 (A. marina 11017) exceptionally uses chlorophyll d as the main photosynthetic pigment absorbing longer wavelength light than the canonical pigment, chlorophyll a, indicating existence of a system to sense longer wavelength light than others. On the other hand, A. marina 11017 has the PBS apparatus to harvest short-wavelength orange light, similar to most cyanobacteria. Thus, A. marina 11017 might sense longer wavelength light and harvest shorter wavelength light by using bilin pigments. Phycocyanobilin (PCB) is the main bilin pigment of both systems. Phycocyanobilin:ferredoxin oxidoreductase (PcyA) catalyzes PCB synthesis from biliverdin via the intermediate 18(1),18(2)-dihydrobiliverdin (18(1),18(2)-DHBV), resulting in the stepwise shortening of the absorbing wavelengths. In this study, we found that A. marina 11017 exceptionally encodes two PcyA homologs, AmPcyAc and AmPcyAp. AmPcyAc is encoded on the main chromosome with most photoreceptor genes, whereas AmPcyAp is encoded on a plasmid with PBS-related genes. High accumulation of 18(1),18(2)-DHBV for extended periods was observed during the reaction catalyzed by AmPcyAc, whereas 18(1),18(2)-DHBV was transiently accumulated for a short period during the reaction catalyzed by AmPcyAp. CBCRs could sense longer wavelength far-red light through 18(1),18(2)-DHBV incorporation, whereas PBS could only harvest orange light through PCB incorporation, suggesting functional diversification of PcyA as AmPcyAc and AmPcyAp to provide 18(1),18(2)-DHBV and PCB to the light perception and harvesting systems, respectively.