Pharaonis Phoborhodopsin (ppR), which is a photo receptor for negative phototaxis in Natoronomonas pharaonis, consists of a 7 helical-transmembrane protein with a retinal choromophore linke to Lys205 through protonated Schiff base. To understand the signal transduction mechanism, it is important to investigate the protein conformational change with retinal photoisomerization. We previously observed 13C signals of functional photointermediates and change in protein dynamics in ppR by in-situ photo-irradiation solid-state MAS NMR [1,2]. Here we present a 13C MAS SSNMR study of retinal-protein interactions in ppR. We prepared [15, 20-13C]retinal, [Cζ-13C]Tyr and [Cε-13C]Lys-labeled ppR within the EggPC lipid bilayer to investigate the conformation of residues in the vicinity of retinal. The correlated peaks of Cζ-Tyr174 with retinal were appeared in 2D PDSD (proton-driven spin-diffusion) NMR spectra. The site-specific 13C chemical shifts have revealed interesting information about retinal-binding site. We will discuss the change of protein conformation near retinal chromophore compared to the peaks of its mutants.
[1] Y. Tomonaga et al. (2011) Biophys. J. 101 L50-L52.
[2] I. Kawamura et al. (2008) Photochem. Photobiol. 85 921-930.