Cyanobacterial phytochrome-like PixJ1 holoprotein shows novel reversible photoconversion between blue- and green-absorbing forms
Cyanobacterial phytochrome-like PixJ1 holoprotein shows novel reversible photoconversion between blue- and green-absorbing forms
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DOI：
10.1093/pcp/pch214
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发表时间：
2004-12-01
影响因子：
4.9
通讯作者：
Ikeuchi, M
中科院分区：
文献类型：
--
作者：
Yoshihara, S;Katayama, M;Ikeuchi, M
该基因 pixJ1（以前称为 pisJ1）预计会编码一种光敏色素样光感受器，该感受器对于单细胞蓝藻集胞藻属的正趋光性至关重要。 PCC 6803 [吉原等人。 （2000）植物细胞生理学。 41：1299]。 PixJ1 蛋白作为与多聚组氨酸标签 (His-PixJ1) 的融合体过表达，并从集胞藻细胞中分离出来。锌荧光测定表明线性四吡咯作为发色团共价连接到 His-PixJ1 蛋白上。 His-PixJ1 在蓝色光吸收形式（P-b，lambda(Amax) = 425-435 nm）和绿色光吸收形式（P-g，lambda(Amax) = 535 nm）之间表现出新型光可逆转换。黑暗孵育导致 P-g 恢复为 P-b，表明 P-b 形式在黑暗中的稳定性。红光或远红光照射对已知光敏色素的光化学转化有效，但 P-b 和 P-g 形式的光谱没有产生变化。定点诱变揭示 PixJ1 第二个 GAF 结构域中的 Cys-His 基序负责发色团的结合。关于新型光转换光谱讨论了可能的发色团种类。
The gene, pixJ1 (formerly pisJ1), is predicted to encode a phytochrome-like photoreceptor that is essential for positive phototaxis in the unicellular cyanobacterium Synechocystis sp. PCC 6803 [Yoshihara et al. (2000) Plant Cell Physiol. 41: 1299]. The PixJ1 protein was overexpressed as a fusion with a poly-histidine tag (His-PixJ1) and isolated from Synechocystis cells. A zinc-fluorescence assay suggested that a linear tetrapyrrole was covalently attached to the His-PixJ1 protein as a chromophore. His-PixJ1 showed novel photoreversible conversion between a blue light-absorbing form (P-b, lambda(Amax) = 425-435 nm) and a green light-absorbing form (P-g, lambda(Amax) = 535 nm). Dark incubation led P-g to revert to P-b, indicative of stability of the P-b form in darkness. Red or far-red light irradiation, which is effective for photochemical conversion of the known phytochromes, produced no change in the spectra of P-b and P-g forms. Site-directed mutagenesis revealed that a Cys-His motif in the second GAF domain of PixJ1 is responsible for binding of the chromophore. Possible chromophore species are discussed with regard to the novel photoconversion spectrum.