The blue-light receptor YtvA acts in the environmental stress signaling pathway of Bacillus subtilis

Journal of bacteriology, (2006) 188(17), 6387–95

Speaker：葉駿達                                                Date：2007/03/07 13:10~14:00

Commentator：吳俊忠老師                     Place：Room 601

Abstract：

  There are several mechanisms against general stresses in Bacillus subtilis and related gram-positive bacteria, one of which is controlled by the signal transcriptional factor σ^B via a network called “partner-switching” mechanism. This network contains five paralogous proteins that function as negative regulators and the signal is transduced by serine or threonine phosphorylation of the proteins (1). When under stress, the phosphatase of the bacterial cell is activated by its activators and dephosphorylates the downstream anti-anti-σ factor. The dephosophorylated anti-anti-σ then binds the anti-σ factor to release σ^B, which in turn initiates the transcription of target genes (2). In this study the authors demonstrated that YtvA, the sixth paralog, was a positive regulator in the same environmental signal branch. YtvA contains a blue-light-sensing domain, called light-oxygen-voltage (LOV) domain, similar to those found in phototropins, the signaling proteins of plants. They found that YtvA and at least three of the negative regulators can form a large environmental signaling complex. In YtvA the cysteine 62 residue of LOV domain, which has been shown to be critical for FMN (flavin monouncleotide)-C4 adduct formation in related blue-light photoreceptors, is required for the regulator activity under environmental stresses. In addition, this organism has some ways, like Spx regulator of disulfide stress, to alter ytvA expression more subtly. These results support a model in which the multiple environmental signals are integrated in a signaling complex to modulate the general stress response.

References：

(1) Dufour, A., and W. G. Haldenwang. 1994. Interactions between a Bacillus subtilis anti-σ factor (RsbW) and its antagonist (RsbV). J. Bacteriol. 176:1813-1820.

(2) Kim, T. J., T. A. Gaidenko, and C. W. Price. 2004. A multicomponent protein complex mediates environmental stress signaling in Bacillus subtilis. J. Mol. Biol. 341:135-150