orals 5th Asia-Pacific NMR Symposium 2013

Stabilised GPCRs for solution NMR-based dynamics studies (#20)

Fabian Bumbak 1 2 , Daniel J Scott 1 2 , Ross AD Bathgate 1 2 , Paul R Gooley 2
  1. The Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
  2. Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, VIC, Australia

G-protein coupled receptors (GPCRs) are pivotal in ligand-induced signal transduction across the cell membrane and hence represent major drug targets. Signal transduction requires an apparent conformational rearrangement of the GPCR’s seven trans-membrane helices. GPCRs are highly dynamic and constantly scan a set of discrete conformational states that coexist in equilibrium. It is currently believed that binding of ligands shifts the equilibrium towards distinct conformations that are thermodynamically favourable. Recently, technological advances have led to crystal structures of 18 different GPCRs, providing invaluable insights into GPCR structure and function. However, each structure is a snapshot of one of many possible receptor conformations, most likely representing a conformation frozen at a thermodynamic minimum favourable for crystallisation. It is desirable to complement these achievements by probing conformational dynamics and identifying conformations mediating particular signalling responses. We aim to apply solution NMR spectroscopy to assess the dynamic landscape of 13CH3-methionine labelled rat Neurotensin receptor 1 (rNTS1). Using Cellular High-throughput Encapsulation, Solubilisation and Screening (CHESS)1 , we engineered a stabilised version of rNTS1 that is stable in harsh detergents for days, rendering this protein accessible to solution NMR studies. Sufficient quantities of engineered rNTS1 were obtained from E. coli cultures grown in shake flasks containing defined medium. Methionine pathway inhibition was applied to promote incorporation of site-specific labels. The receptor was reconstituted in n-decyl-β-D-maltopyranoside micelles and purified using immobilised-metal affinity chromatography followed by size exclusion chromatography. Using 1H-13C SOFAST-HMQC we have identified 7 methionine resonances which we will assign using site-directed mutagenesis. We will analyse line-shape and chemical shift changes in the presence and absence of ligands to explore the changes in conformation and dynamics of this receptor.

  1. Scott, D. J., and A. Pluckthun. 2013. Direct molecular evolution of detergent-stable G protein-coupled receptors using polymer encapsulated cells. J Mol Biol 425:662-677.