What is the function of clathrin in protein trafficking?

Clathrin plays a crucial role in the process of endocytosis, particularly in the formation of vesicles that transport proteins and other molecules within cells. When clathrin coats the cytoplasmic side of the plasma membrane, it facilitates the invagination of the membrane, leading to the budding off of a vesicle. This vesicle can then carry proteins destined for various locations inside the cell or even for secretion outside the cell.

The process begins with the assembly of clathrin triskelions, which are the basic structural units made up of three heavy chains and three light chains. These triskelions form a basket-like structure around the emerging vesicle, helping maintain its shape and stability as it detaches from the membrane. This mechanism is vital for efficient protein trafficking, as it ensures that proteins are effectively packaged and directed to their ultimate destinations, such as lysosomes, endosomes, or the Golgi apparatus for further processing and sorting.

Understanding the specific role of clathrin in the formation of vesicles clarifies its importance in the broader context of cellular function and protein trafficking, distinguishing it from other cellular processes like degradation of proteins, cell division, or ribosome formation.