Structural characterization of the light activated BLUF photoreceptor PAC

Photoreceptors containing a Blue-Light sensor Using Flavin (BLUF) are highly attractive for a broad range of applications. In this project, a photoactivated adenylate cyclase (PAC) containing a BLUF sensor domain coupled to an adenylyl cyclase (AC) effector domain is studied. For this, PAC protein was produced, purified and characterized. Structural changes around the FMN chromophore could be elucidated using time-resolved crystallography (TRX). However, structural changes happening in the AC domain could not be observed using crystallographic techniques as the crystal packing is preventing them. We suspect a bigger conformational change is required to activate the AC domain, which could be confirmed using SAXS. Therefore, the aim of the experiment is to measure SAXS data on PAC in its dark state and compared them with measurements after blue light illumination. Applying SAXS would greatly complement TRX data and would help to understand the entire signaling process of PAC.