Extracellular Domain (ECD) Proteins

Approximately one quarter of the human genome codes for membrane proteins, many of which have central roles in mediating how cells interact with their surroundings. Well-known examples of membrane proteins include transporters such as ion channels, solute carrier (SLC) proteins, and ATP-binding cassette (ABC) transporters, as well as various cell adhesion molecules (CAMs) and cell surface receptors. The critical importance of membrane proteins has led to them being targeted by more than half of all approved drugs, some of which modulate membrane protein function while others use membrane proteins for targeting specific cell types. For example, Rituximab is a therapeutic monoclonal antibody that recognizes and binds the B-cell specific membrane protein CD20, resulting in the destruction of malignant B cells via mechanisms including antibody-dependent cell-mediated cytotoxicity (ADCC). Membrane proteins can be broadly classified as peripheral or integral based on how they interact with the membrane. Peripheral membrane proteins associate only temporarily with the membrane, either through protein-lipid head group interactions or by coupling with integral membrane proteins. These types of membrane proteins can usually be extracted fairly easily by changing the surrounding ion concentration. Integral membrane proteins are instead permanently attached to the membrane, either at one side (integral monotopic proteins) or spanning the entire membrane (transmembrane proteins). Extracting transmembrane proteins is especially challenging due to the hydrophobic nature of the membrane spanning domains, which makes it difficult to obtain these biomolecules in a pure, active form. Many of the drugs developed against membrane proteins are directed toward the extracellular domains, since it is these regions that most often interact with other cells or signaling molecules. Purified extracellular domain proteins therefore have broad utility, which includes their use as immunogens for antibody drug development, reagents for CAR-T positive cell monitoring, and antigens for antibody screening and functional testing, as well as tools for characterizing antibody affinities and kinetics, and raw materials for screening compound libraries. To support these types of applications, we provide over 1,000 extracellular domain proteins. These are manufactured using a HEK293 mammalian cell expression system to ensure close-to-native structures and post-translational modifications (PTMs), and each batch undergoes rigorous purity and stability testing.