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A Phytochrome‐like Protein AphC Triggers the cAMP Signaling Induced by Far‐red Light in the Cyanobacterium Anabaena sp. Strain PCC7120 ¶
Author(s) -
Okamoto Shinobu,
Kasahara Masahiro,
Kamlya Asako,
Nakahira Yuka,
Ohmori Masayuki
Publication year - 2004
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.2004.tb00109.x
Subject(s) - phytochrome , open reading frame , far red , biology , pas domain , mutant , biochemistry , anabaena , signal transduction , cyclase , red light , cyanobacteria , gene , enzyme , botany , genetics , transcription factor , peptide sequence , bacteria
In the filamentous, nitrogen‐fixing cyanobacterium Anabaena sp. PCC7120, red light (630 nm) decreased, whereas far‐red light (720 nm) increased cellular adenosine 3′,5′‐cyclic monophosphate (cAMP) content. To find a red and far‐red light photoreceptor that triggers the cAMP signal cascade, we disrupted 10 open reading frame having putative chromophore‐binding GAF domains. The response of the cellluar cAMP concentration to red and far‐red light in each open reading frame disruptant was determined. It was found that only the mutant of the gene all2699 failed to respond to far‐red light. The open reading frame named as aphC encoded a protein with 920 amino acids including GAF domains similar to those involved in Cph2, a photoreceptor of Synechocystis sp. PCC6803. To determine which adenylate cyclase (AC) is responsible for far‐red light signal, we disrupted all AC genes and found that CyaC was the candidate. The enzymatic activity of CyaC might be controlled by a far‐red light photoreceptor through the phosphotransfer reaction. The site‐specific mutant of the Asp59 residue of the receiver (R1) domain of CyaC lost its light‐response capability. It was suggested that the far‐red light signal was received by AphC and then transferred to the N‐terminal response regulator domain of CyaC. Then its catalytic activity was stimulated, which increased the cellular cAMP concentration and drove the subsequent signal transduction cascade.