Figure 2. Membrane protein structural biology.

Membrane proteins need to be extracted from their membranes using detergent solubilisation. Membrane protein crystallisation is difficult and often requires protein engineering to remove flexible loops and sugar. Cryo-EM structure determination allows direct imaging of membrane proteins in detergents or in more natural environments like nano-discs. The presence of sugars or very large membrane complexes does not preclude cryo-EM structure determination. The structures of the photosystem II - light harvesting supercomplex⁶⁰, TRPV1 in complex with a spider toxin⁴², gamma-secretase³³, the voltage-gated calcium channel CaV1.1⁴³, the glycine receptor⁴⁵, and bovine complex-I⁵⁹ are shown as examples.