The roles of the chaperone-like protein CpeZ and the phycoerythrobilin lyase CpeY in phycoerythrin biogenesis
The roles of the chaperone-like protein CpeZ and the phycoerythrobilin lyase CpeY in phycoerythrin biogenesis
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DOI：
10.1016/j.bbabio.2019.06.001
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发表时间：
2019-07-01
影响因子：
4.3
通讯作者：
Schluchter, Wendy M.
中科院分区：
文献类型：
--
作者：
Kronfel, Christina M.;Biswas, Avijit;Schluchter, Wendy M.
藻红蛋白(PE)存在于双虹吸藻Fremyella diplosiphon(Tolypothrix sp.PCC7601)含有五个藻红胆素(PEB)发色团，与六个半胱氨酸残基相连，可有效捕捉绿光进行光合作用。PE亚基上的发色团连接是通过胆红素裂解酶催化的反应进行的，但对所有胆红素裂解酶在藻红蛋白中的作用的表征还不完整。为了更全面地了解CpeZ和CpeY在蓝藻PE生物发生中的个体功能，我们研究了从野生型双虹吸藻、cpeZ和cpeY基因敲除突变体中纯化的PE和藻胆体。我们发现，cpeZ和cpeY突变体比野生型细胞积累更少的PE。我们发现，在cpeZ突变体中，PE的两个亚基的发色作用都受到了影响，特别是PE的β亚基CPEB的Cys-80和Cys-48/Cys-59位点。CpeY突变体在CPEA的Cys-82处表现出较低的着色素化。我们还表明，在体外，CpeZ稳定PE亚基，并帮助CPEB变性后的折叠。综上所述，我们得出结论，CpeZ作为一种伴侣样蛋白，帮助PE亚基的折叠/稳定，允许胆碱裂解酶如CpeY和CPE将PEB连接到它们的PE亚基上。
Phycoerythrin (PE) present in the distal ends of light-harvesting phycobilisome rods in Fremyella diplosiphon (Tolypothrix sp. PCC 7601) contains five phycoerythrobilin (PEB) chromophores attached to six cysteine residues for efficient green light capture for photosynthesis. Chromophore ligation on PE subunits occurs through bilin lyase catalyzed reactions, but the characterization of the roles of all bilin lyases for phycoerythrin is not yet complete. To gain a more complete understanding about the individual functions of CpeZ and CpeY in PE biogenesis in cyanobacteria, we examined PE and phycobilisomes purified from wild type F. diplosiphon, cpeZ and cpeY knockout mutants. We find that the cpeZ and cpeY mutants accumulate less PE than wild type cells. We show that in the cpeZ mutant, chromophorylation of both PE subunits is affected, especially the Cys-80 and Cys-48/Cys-59 sites of CpeB, the beta-subunit of PE. The cpeY mutant showed reduced chromophorylation at Cys-82 of CpeA. We also show that, in vitro, CpeZ stabilizes PE subunits and assists in refolding of CpeB after denaturation. Taken together, we conclude that CpeZ acts as a chaperone-like protein, assisting in the folding/stability of PE subunits, allowing bilin lyases such as CpeY and CpeS to attach PEB to their PE subunit.