Primary and Secondary Photodynamics of the Violet/Orange Dual-Cysteine NpF2164g3 Cyanobacteriochrome Domain from Nostoc punctiforme

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• 作者：Sean M. Gottlieb ; Peter W. Kim ; Scott C. Corley ; Dorte Madsen ; Samuel J. Hanke ; Che-Wei Chang ; Nathan C. Rockwell ; Shelley S. Martin ; J. Clark Lagarias ; Delmar S. Larsen
• 刊名：Biochemistry
• 出版年：2014
• 出版时间：February 18, 2014
• 年：2014
• 卷：53
• 期：6
• 页码：1029-1040
• 全文大小：877K
• ISSN：1520-4995

文摘

Cyanobacteriochromes (CBCRs) are cyanobacterial photoreceptors distantly related to phytochromes. Like phytochromes, CBCRs photointerconvert between two photostates that accompany photoisomerization of their bilin chromophores. While phytochromes typically exhibit red/far-red photocycles, CBCR photocycles are much more diverse, spanning the near-ultraviolet and the entire visible region. All CBCRs described to date have a conserved Cys residue covalently attached to the linear tetrapyrrole (bilin) chromophore; two CBCR subfamilies also exploit a second thioether linkage to the chromophore for detection of near-ultraviolet to blue light. Here, we present the photodynamic analysis of the insert-Cys CBCR NpF2164g3, a representative of the second class of two-cysteine CBCRs. Using broadband transient absorption pump鈥損robe spectroscopy, we characterize the primary (100 fs to 10 ns) and secondary (10 ns to 1 ms) photodynamics in both directions, examining photodynamics over nine decades of time. Primary isomerization dynamics occur on a 10 ps time scale for both forward and reverse reactions. In contrast to previous studies on Tlr0924, a representative of the other class of two-cysteine CBCRs, formation and elimination of the second linkage are slower than the 1 ms experimental range probed here. These results extend our understanding of dual-cysteine CBCR photocycles in the phytochrome superfamily.