Understanding Structural and Functional Stability of two Rhomboid Proteases: HiGlpG and PsAarA

Abstract

Solid-state 2 H NMR spectra were acquired for different tilt angles of the aligned samples. The methyl group orientations relative to the membrane normal were calculated by fitting the experimental 2 H NMR spectra using a static uniaxial distribution [3] for the protein embedded within lipid bilayers. We found that the orientation of the C9-methyl group obtained from 2 H NMR spectroscopy was similar to that from X-ray data. By contrast, the orientations of the C5-and C13-methyl groups were different versus the X-ray crystal structures. The retinal structure was analyzed using the three-plane model, as in previous studies of rhodopsin in the dark and the Meta-I states [4]. Moreover, a new approach was tested that combines 2 H NMR and X-ray restraints for retinal together with the rhodopsin binding-pocket using simulated annealing. Our results yield new insights into formation of the activated state of the receptor in lipid membranes. [1] A.V. Struts et al. (2011) Nat.