A Second Photochromic Bacteriophytochrome from Synechocystis sp. PCC 6803: Spectral Analysis and Down-Regulation by Light
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- 作者：Chung-Mo Park ; Jeong-Il Kim ; Song-Sook Yang ; Jeong-Gu Kang ; Jin-Ho Kang ; Jae-Yoon Shim ; Young-Ho Chung ; Young-Mok Park ; and Pill-Soon Song
- 刊名：Biochemistry
- 出版年：2000
- 出版时间：September 5, 2000
- 年：2000
- 卷：39
- 期：35
- 页码：10840 - 10847
- 全文大小：147K
- 年卷期：v.39,no.35(September 5, 2000)
- ISSN：1520-4995
文摘
It now appears that photosynthetic prokaryotes and lower eukaryotes possess higher plantphytochrome-like proteins. In this work, a second phytochrome-like gene was isolated, in addition to therecently identified Cph1 phytochrome, from the Synechocystis sp. PCC 6803, and its gene product wascharacterized photochemically. The open reading frame sll0821 (designated cph2 in this work) has structuralcharacteristics similar to those of the plant phytochromes and the Synechocystis Cph1 with high aminoacid sequence homology in the N-terminal chromophore binding domain. The predicted Cph2 proteinconsists of 1276 amino acids with a calculated molecular mass of 145 kDa. Interestingly, the Cph2 proteinhas two putative chromophore binding domains, one around Cys-129 and the other around Cys-1022.The Cph2 was overexpressed in E. coli as an Intein/CBD (chitin binding domain) fusion and in vitroreconstituted with phycocyanobilin (PCB) or phytochromobilin (P
B). Both the Cph2-PCB and Cph2-PB adducts showed the typical photochromic reversibility with the difference spectral maxima at 643/690 and 655/701 nm, respectively. The Cys-129 was confirmed to be the chromophore binding residueby in vitro mutagenesis and Zn2+ fluorescence. The microenvironment of the chromophore in Cph2 seemsto be similar to that in plant phytochromes. The cph2 gene expression was dark-induced and down-regulated to a basal level by light, like the cph1 gene. These observations suggest that Synechocystisspecies have multiple photosensory proteins, probably with distinct roles, as in higher plants.
B). Both the Cph2-PCB and Cph2-PB adducts showed the typical photochromic reversibility with the difference spectral maxima at 643/690 and 655/701 nm, respectively. The Cys-129 was confirmed to be the chromophore binding residueby in vitro mutagenesis and Zn2+ fluorescence. The microenvironment of the chromophore in Cph2 seemsto be similar to that in plant phytochromes. The cph2 gene expression was dark-induced and down-regulated to a basal level by light, like the cph1 gene. These observations suggest that Synechocystisspecies have multiple photosensory proteins, probably with distinct roles, as in higher plants.