What type of structure does glycophorin A (GPA) have?

Glycophorin A (GPA) is a glycoprotein found in the membranes of red blood cells, specifically known for its role in maintaining cell integrity and preventing aggregation. The structure of GPA is characterized by having a single transmembrane segment.

This transmembrane segment allows the protein to span the lipid bilayer of the cell membrane, with one part of the protein residing in the extracellular space and the other anchored within the hydrophobic core of the membrane. The extracellular domain of GPA is quite large and contributes to its function by facilitating cell-cell interactions and maintaining the negative charge on the surface of red blood cells, which is essential for preventing their aggregation in the bloodstream.

The presence of just one transmembrane segment is a distinctive feature that differentiates GPA from proteins that may have multiple transmembrane domains, which typically have more complex topologies and functions. Therefore, understanding these structural characteristics is crucial for appreciating how GPA functions within the cellular environment.