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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Phytochrome from Agrobacterium tumefaciens has unusual spectral properties and reveals an N-terminal chromophore attachment site
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Phytochrome from Agrobacterium tumefaciens has unusual spectral properties and reveals an N-terminal chromophore attachment site

机译：来自根癌农杆菌的植物色素具有不同寻常的光谱特性，并揭示了一个N端发色团附着位点

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摘要

Phytochromes are photochromic photoreceptors with a bilin chromophore that are found in plants and bacteria. The soil bacterium Agrobacterium tumefaciens contains two genes that code for phytochrome-homologous proteins, termed Agrobacterium phyto-chrome 1 and 2 (Agp1 and Agp2). To analyze its biochemical and spectral properties, Agp1 was purified from the clone of an E. coli overexpressor. The protein was assembled with the chromophores phycocyanobilin and biliverdin, which is the putative natural chromophore, to photoactive holoprotein species. Like other bacterial phytochromes, Agp1 acts as light-regulated His kinase. The biliverdin adduct of Agp1 represents a previously uncharacterized type of phytochrome photoreceptor, because photoreversion from the far-red absorbing form to the red-absorbing form is very inefficient, a feature that is combined with a rapid dark reversion. Biliverdin bound covalently to the protein; blocking experiments and site-directed mutagenesis identified a Cys at position 20 as the binding site. This particular position is outside the region where plant and some cyanobacterial phytochromes attach their chromophore and thus represents a previously uncharacterized binding site. Sequence comparisons imply that the region around Cys-20 is a ring D binding motif in phytochromes.
机译：植物色素是一种在植物和细菌中发现的具有Bilin生色团的光致变色感光体。土壤细菌根癌土壤杆菌包含两个编码植物色素同源蛋白的基因，分别称为土壤杆菌植物色素1和2（Agp1和Agp2）。为了分析其生化和光谱特性，从大肠杆菌过表达子的克隆中纯化了Agp1。该蛋白与生色团藻蓝蛋白和公认的天然生色团biliverdin组装成光活性全蛋白。像其他细菌性植物色素一样，Agp1充当光调节的His激酶。 Agp1的biliverdin加合物代表了以前未表征的植物色素感光体，因为从远红吸收形式到红吸收形式的光转换效率很低，这是一种与快速暗转换结合的功能。 Biliverdin与蛋白质共价结合；阻断实验和定点诱变将20位的Cys鉴定为结合位点。该特定位置在植物和某些蓝细菌植物色素附着其发色团的区域之外，因此代表了以前未表征的结合位点。序列比较表明，Cys-20周围的区域是植物色素中的D环结合基序。

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