Fig. 1: Three active-site conformations, including the central FMN, Gln, and Tyr, as well as the nearby Trp in BLUF domains.
From: Origin of the multi-phasic quenching dynamics in the BLUF domains across the species
Three active-site conformations, including the central FMN (gray), Gln (Q, cyan/green/yellow), and Tyr (Y, gray), as well as the nearby Trp (W, cyan/green/yellow) in BLUF domains. WinNHin configuration (a) is adopted from one X-ray structure of the AppA BLUF domain (PDB: 1YRX). A preferred no-proton relay geometry of Tyr and Gln is depicted according to previous free energy calculations17. WinNHout (b) and Wout (c) configurations are adopted from the two subunits of SyPixD tetramer (PDB: 2HFO), chain D, and chain B, respectively. Both favor a proton transfer geometry where Tyr OH is H bonded to Gln Oε1, and Gln Nε2H is H bonded to FMN N517,25. Edge-to-edge distances (double arrows) between the nearby Trp and FMN are shown in each configuration. Possible proton transfer pathways are drawn in dashed lines.
