Photoconversion Mechanisms of the Green/Red Photoreceptor Cyanobacteriochrome AnPixJ Studied by Time-resolved Spectroscopy

Abstract

Cyanobacteriochromes are novel phytochrome-like photoreceptor proteins containing GAF domain. SyPixJ1 (sll0041) of Synechocystis sp. PCC6803 was shown to regulate the phototaxis of cells. We studied AnPixJ-GAF2 of Anabaena sp. PCC7120 that shows a photochromism between the green-light absorbing form (Pg, 543 nm) and the red-light absorbing form (Pb, 649 nm). The light-signal conversion process and the regulation mechanisms of absorption spectra are unknown. We investigated the photoreaction by the time-resolved absorption spectroscopy and global analysis. The reaction process from Pg to Pb showed two kinetic components between micro and millisecond time range. The conversions from Pb to Pg showed one kinetic components at millisecond time range. We will discuss the structural-change models based on the absorption peaks of the intermediates obtained by global analysis.