A rising tide of blue-absorbing biliprotein photoreceptors – characterization of seven such bilin-binding GAF domains in Nostoc sp. PCC7120

摘要: Cyanobacteriochromes are photochromic sensory photoreceptors in cyanobacteria that related to phytochromes but cover a much broader spectral range. Using homology search, group of putative blue-absorbing was identified Nostoc sp. PCC 7120 that, addition the canonical chromophore-binding cysteine cyanobacteriochromes, have conserved extra DXCF motif. To assess their photochemical activities, GAF domains were expressed Escherichia coli together with genes for phycocyanobilin biosynthesis. All except one covalently bound chromophore and showed photoreversible responses, absorption at approximately 420 nm 15Z states formed dark, variety red-shifted peaks 490–600 nm range 15E after light activation. Under denaturing conditions, chromophores as phycocyanobilin, phycoviolobilin or mixtures both. The cysteines those motifs mutated, singly together. is responsible stable covalent attachment bilin apo-protein C31. second linkage from motif, probably C10 chromophore, yields rubin-type chromophores, lost most cases upon photoconversion isomers also when denatured acidic urea.