Biochemical and Physiological Characterization of a BLUF Protein−EAL Protein Complex Involved in Blue Light-Dependent Degradation of Cyclic Diguanylate in the Purple Bacterium Rhodopseudomona

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• 作者：Takuya Kanazawa ; Shukun Ren ; Mikika Maekawa ; Koji Hasegawa ; Fumio Arisaka ; Mamoru Hyodo ; Yoshihiro Hayakawa ; Hiroyuki Ohta ; Shinji Masuda
• 刊名：Biochemistry
• 出版年：2010
• 出版时间：December 21, 2010
• 年：2010
• 卷：49
• 期：50
• 页码：10647-10655
• 全文大小：950K
• 年卷期：v.49,no.50(December 21, 2010)
• ISSN：1520-4995

文摘

Organisms adapt their physiologies in response to the quality and quantity of environmental light. Members of a recently identified photoreceptor protein family, BLUF domain proteins, use a flavin chromophore to sense blue light. Herein, we report that PapB, which contains a BLUF domain, controls the biofilm formation of the purple photosynthetic bacterium Rhodopseudomonas palustris. Purified PapB undergoes a typical BLUF-type photocycle, and light-excited PapB enhances the phosphodiesterase activity of the EAL domain protein, PapA, which degrades the second messenger, cyclic dimeric GMP (c-di-GMP). PapB directly interacts with PapA in vitro in a light-independent manner and induces a conformational change in the preformed PapA−PapB complex. A PapA−PapB docking simulation, as well as a site-directed mutagenesis study, identified amino acids partially responsible for the interaction between the PapA EAL domain and the two C-terminal α-helices of the PapB BLUF domain. Thus, the conformational change, which involves the C-terminal α-helices, transfers the flavin-sensed blue light signal to PapA. Deletion of papB in R. palustris enhances biofilm formation under high-intensity blue light conditions, indicating that PapB functions as a blue light sensor, which negatively regulates biofilm formation. These results demonstrate that R. palustris can control biofilm formation via a blue light-dependent modulation of its c-di-GMP level by the BLUF domain protein, PapB.