Cationic Amino Acid Transport Proteins (CAT proteins) are a group of membrane transport proteins that facilitate the uptake of cationic amino acids across cell membranes. These proteins play a crucial role in maintaining cellular homeostasis by regulating the intracellular concentration of essential cationic amino acids such as arginine, lysine, and ornithine.
CAT proteins are primarily found in the plasma membrane of various cell types, including epithelial cells, neurons, and immune cells. They are characterized by their ability to bind and transport cationic amino acids through facilitated diffusion, utilizing the electrochemical gradient across the cell membrane.
Cationic amino acids are positively charged due to their amino group, and they cannot passively diffuse across the lipid bilayer of the cell membrane. CAT proteins provide a specific pathway for their transport by binding to them and conformationally changing to allow their translocation into the cell.
These transport proteins are highly selective, exhibiting different affinities for different cationic amino acids. They may also vary in their tissue distribution, expression levels, and affinity for other molecules. Some CAT proteins, for instance, can transport both cationic amino acids and certain drugs, highlighting their role in drug uptake and disposition.
The activity of CAT proteins is regulated through various mechanisms, including gene expression, phosphorylation, and protein-protein interactions. Dysregulation or mutations in CAT proteins have been linked to several physiological and pathological conditions, such as neurodegenerative diseases, aminoacidurias, and certain cancers. Therefore, understanding the structure and function of cationic amino acid transport proteins is vital for elucidating their role in cellular processes and developing therapeutic strategies targeting these proteins.
