Table 1 Comparison of GPCR expression systems for NMR studies

Table adapted from Tapaneeyakorn, S., Goddard, A.D., Oates, J., Willis, C.L. and Watts, A. (2011) Solution- and solid-state NMR studies of GPCRs and their ligands. Biochim. Biophys. Acta 1808, 1462–1475 with permission.

Expression systemAdvantagesDisadvantages
E. coliInexpensiveLack of post-translational modification, e.g. glycosylation is required for some GPCR–ligand interactions
Ease of cultureLack of some eukaryotic membrane components including cholesterol can affect receptor activity
Genetic flexibilityHigh-level expression may result in formation of inclusion bodies; limited success in refolding GPCRs
Strains optimized for protein expressionDifferent codon usage (overcome by expression of rare tRNAs)
Very flexible isotope labelling strategiesLow success rate of active GPCR expression
High scalability, although there is not necessarily a linear relationship between scale and yield
YeastInexpensiveEndogenous GPCRs and G-proteins which may interfere with expression and purification
Ease of cultureDifferent membrane composition
Genetic flexibilityRelatively thick cell wall may impede purification
Good scalabilityLabelling strategies more limited than some systems
Cellular compartmentalization
Eukaryotic post-translational modifications
Can co-express accessory proteins
Baculovirus/insect cellsEukaryotic; nearly all post-translational modifications are identical with those of mammalian cellsGlycosylation is different from that of animal cells
Most GPCRs expressed are activeMembrane is higher in unsaturated fatty acids and lower in cholesterol which can be key in GPCR activity
Insect cells are semi-adherent and also grow in suspension allowing good scalability, e.g. fermenter growthsRequires high virus titre
Commercialization has reduced costsCultures are only stable for ~1 month owing to accumulation of defective virus particles
Limited labelling strategies available
Mammalian cellsNative cellular environmentRelatively expensive
Correct trafficking and foldingPossible complications from endogenous receptors and signalling components
Correct membrane environmentDifficult to scale
Correct post-translational modificationFew labelling strategies available
Most GPCRs expressed are active
Cell-free expressionOnly the protein of interest is producedPoor scalability
Can express toxic proteinsYields >1 mg/ml reaction
Can include detergents and membrane mimeticsMay require optimization of detergents and membrane mimetics
Relatively expensiveLow success rate of GPCR expression to date
Complete labelling control