Lessons Learned on the Path to Solution NMR of the GlpG Rhomboid Protease

Rhomboids constitute a broad family of intramembrane serine proteases found in all kingdoms of life, participating in a diverse array of biological processes. High-resolution structures of the catalytic transmembrane domain of the E. coli GlpG rhomboid have revealed that hydrolytic cleavage is carried out in an active site that sits below the membrane surface. However, questions remain regarding how the transmembrane substrate gains access to catalytic residues, with some suggesting that conformational dynamics involving transmembrane segments could allow lateral entry from the lipid phase. Solution NMR has the potential to address this question by characterizing conformational dynamics at atomic resolution; however, it can be challenging to find conditions that give rise to reasonable spectra. In this talk progress made towards this goal will be presented, along with new insights into the effect of the environment and extramembraneous domains on rhomboid activity arising from this work.