Final answer:
Clathrin triskelia are connected to membrane receptors via adaptor protein 1 (AP1), which plays a crucial role in the formation of clathrin-coated pits during receptor-mediated endocytosis.
Step-by-step explanation:
Clathrin triskelia are connected to membrane receptors via the protein adaptor protein 1 (AP1).
Clathrin is a key protein involved in the formation of coated pits and vesicles during receptor-mediated endocytosis. The process begins when substances to be internalized bind to membrane receptors, resulting in the formation of a coated pit. These coated pits, which are essential for transporting substances into the cell, require clathrin to form their structure.
The linkage between clathrin and the membrane receptors is facilitated by adaptor proteins, specifically adaptor protein 1 (AP1). AP1 not only helps recruit clathrin to the sites of endocytosis but also plays a crucial role in selecting the cargo proteins that will be internalized by the cell. In this context, clathrin and AP1 are crucial for creating the clathrin-coated vesicles that transport selected molecules across the cell membrane.