Phytochrome assembly. The structure and biological activity of 2(R),3(E)-phytochromobilin derived from phycobiliproteins.
Phytochrome assembly. The structure and biological activity of 2(R),3(E)-phytochromobilin derived from phycobiliproteins.
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DOI：
10.1016/s0021-9258(18)42109-6
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发表时间：
1992-07
期刊：
影响因子：
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通讯作者：
J. Cornejo;S. Beale;M. J. Terry;J. Lagarias
中科院分区：
文献类型：
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作者：
J. Cornejo;S. Beale;M. J. Terry;J. Lagarias
单细胞红藻紫球藻和丝状蓝细菌Calothrix sp. PCC 7601含有与藻胆素发色团共价结合的藻胆蛋白。在40 ℃下用甲醇过夜孵育溶剂提取的细胞释放游离藻胆素，所述游离藻胆素通过胆素和脱辅基蛋白之间的硫醚键的甲醇分解裂解而衍生自蛋白质结合的胆素。经比较分光光度法和高压液相色谱法鉴定，其中两种游离胆素分别为3（E）-藻蓝胆素和3（E）-藻红凝血酶胆素。甲醇分解也产生第三个胆色素游离酸，其吸收和1H NMR光谱支持3（E）-phytochromobilin结构的归属。这种新的胆色素是从用含丙酮的溶剂预提取的细胞中分离的主要色素。由于含光敏色素或光敏色素移动素的蛋白质在两种生物中都不存在，因此3（E）-光敏色素移动素必须通过藻胆素发色团的氧化而产生。这种色素不能通过对缺乏藻红蛋白的蓝细菌和红藻进行类似处理而获得。因此，3（E）-phytochromobilin似乎是来自藻红胆素的蛋白质。3（E）-植物色素胆素和3（E）-藻蓝胆素的比较CD光谱表明，这两种胆色素在还原的吡咯环的2-位上共享R立体化学。将2（R），3（E）-光敏色素移动素与重组燕麦脱辅基光敏色素一起孵育产生共价胆色素加合物，该加合物是光活性的并且与从黄化幼苗分离的天然燕麦光敏色素在光谱上不可区分。这些结果证实藻胆蛋白衍生的2（R），3（E）-光敏色素移动素是具有生物活性的光敏色素发色团前体。
The unicellular rhodophyte, Porphyridium cruentum, and the filamentous cyanobacterium, Calothrix sp. PCC 7601, contain phycobiliproteins that have covalently bound phycobilin chromophores. Overnight incubation of solvent-extracted cells at 40 degrees C with methanol liberates free phycobilins that are derived from the protein-bound bilins by methanolytic cleavage of the thioether linkages between bilin and apoprotein. Two of the free bilins were identified as 3(E)-phycocyanobilin and 3(E)-phycoerythrombilin by comparative spectrophotometry and high pressure liquid chromatography. Methanolysis also yields a third bilin free acid whose absorption and 1H NMR spectra support the assignment of the 3(E)-phytochromobilin structure. This novel bilin is the major pigment isolated from cells that are pre-extracted with acetone-containing solvents. Since phytochrome- or phytochromobilin-containing proteins are not present in either organism, the 3(E)-phytochromobilin must arise by oxidation of phycobilin chromophores. This pigment is not obtained by similar treatment of a cyanobacterium and a rhodophyte that lack phycoerythrin. Therefore, 3(E)-phytochromobilin appears to be derived from phycoerythrobilin-containing proteins. Comparative CD spectroscopy of 3(E)-phytochrombilin and 3(E)-phycocyanobilin suggests that the two bilins share the R stereochemistry at the 2-position in the reduced pyrrole ring. Incubation of 2(R),3(E)-phytochromobilin with recombinant oat apophytochrome yields a covalent bilin adduct that is photoactive and spectrally indistinguishable from native oat phytochrome isolated from etiolated seedlings. These results establish that the phycobiliprotein-derived 2(R),3(E)-phytochromobilin is a biologically active phytochrome chromophore precursor.