Probing the Activation Mechanism of Heptahelical Receptors: Experimental Validation of Molecular Dynamics Simulations
Macromolecular complexes, known as ‘signalosomes’, carry chemical signals across cell membranes. For example, heptahelical G protein-coupled receptors (GPCRs) bind to extracellular ligands and couple to a variety of cellular transducer, adaptor and effector proteins. The individual components of GPCR signalosomes have been largely identified, and high-resolution structures are available for many of the cellular proteins and an increasing number of receptors. However, the precise chemical nature of the allosteric coupling between multiple ‘active states’ of ligand-bound receptors and their cellular binding partners is not understood. New approaches are required to probe the complex relationship between structural dynamics and function in GPCR signalosomes. We are advancing an interdisciplinary programme that includes computational modelling and simulations validated by experimental approaches. For example, we have developed a novel amber codon suppression technology to introduce site-specific unnatural amino acids at positions to provide useful chemical handles for subsequent photo-crosslinking or fluorescent tagging. Results from this programme should extend our knowledge of heptahelical receptor function.