Optimizing Membrane Mimetics for Biophysical Studies of a Chimeric Potassium Channel

Membrane proteins (MPs) are embedded in the lipid membrane and mediate cellular communication between the extra- and intra-cellular regions. They represent ~30% of the proteome and more than 40% of drug targets, and yet very few structures of these molecules have been solved. This is because of their strong hydrophobic character that distinguishes them from globular proteins, and leads to unique challenges at all levels, including expression, solubilisation, purification, data collection and structure solution. One of the major challenges of working with membrane proteins is finding a membrane mimetic environment that is conducive to biophysical studies while still maintaining native structure and function. Techniques such as solution NMR have fast-tumbling requirements that are not fulfilled by conventional lipid vesicles. Detergent micelles, isotropic bicelles, and nanodiscs are some of the media available for the solubilization of integral membrane proteins.

The human voltage-gated potassium channel Kv1.3 is upregulated in effector-memory T (T_EM) cells associated with autoimmune diseases, and therefore an important pharmaceutical target. The ShK toxin is a 35-residue polypeptide derived from a sea anemone and found to block Kv1.3 at low picomolar concentration. Deeper insight into the structural basis of channel-toxin complex formation would be pivotal for understanding this interaction, guiding drug design, and ultimately improving pharmaceutical efficacy. In this study we present a membrane mimetics screening effort allowing us to study a chimeric Kv1.3 channel in complex with ShK using NMR methods.