Green Light Sensing System

Cyanobacteriochrome is a group of photoreceptors that are distinct relatives of phytochromes but are found only in cyanobacteria. A putative cyanobacteriochrome, CcaS, is known to chromatically regulate the expression of the phycobilisome linker gene (cpcG2) in Synechocystis sp. PCC 6803 (Hirose et al., 2008). Previous studies have showed the reversible photoconversion between a green-absorbing form (Pg, λmax = 535 nm) and a red-absorbing form (Pr, λmax = 672 nm) of CcaS. Autophosphorylation activity of the histidine kinase domain in the C-terminal region of CcaS is up-regulated by preirradiation with green light (Tabor et al., 2011). Similarly, phosphotransfer to the cognate response regulator, CcaR, is higher in Pr than in Pg. In cyanobacteria,CcaS phosphorylates CcaR under green light and induces expression of cpcG2, leading to accumulation of CpcG2-phycobilisome as a chromatic acclimation system.

File:13SJTU greenlight.gif

Promoter Modification---K1026009

In order to be consistent with other light sensing systems, we did some modification to CcaR-responding promoter. Having noticed that there are six base pairs in the G-box (Hirose et al., 2010) of CpcG2 identical to -35 site of BBa_J23007, we predict CcaR will bind to G-box, therefore preventing RNA polymerase from binding to the promoter. This modification allows down-regulation effect under green light.

5’-CTTTCCGATTTCTTTACGATTTTCTCCGCCCTAGGTATTATGCTAGC-3’

Reference

HIROSE, Y., NARIKAWA, R., KATAYAMA, M. & IKEUCHI, M. 2010. Cyanobacteriochrome CcaS regulates phycoerythrin accumulation in Nostoc punctiforme, a group II chromatic adapter. Proceedings of the National Academy of Sciences, 107, 8854-8859.


HIROSE, Y., SHIMADA, T., NARIKAWA, R., KATAYAMA, M. & IKEUCHI, M. 2008. Cyanobacteriochrome CcaS is the green light receptor that induces the expression of phycobilisome linker protein. Proceedings of the National Academy of Sciences, 105, 9528-9533.


TABOR, J. J., LEVSKAYA, A. & VOIGT, C. A. 2011. Multichromatic control of gene expression in escherichia coli. Journal of Molecular Biology, 405, 315-324.