Final answer:
E-cadherin has five extracellular cadherin (EC) repeats in its extracellular domain, which are crucial for its cell-cell adhesion function.
Step-by-step explanation:
E-cadherin, which is a type of cell adhesion molecule involved in forming adherens junctions, has an important role in binding cells together to form cohesive tissues. The extracellular domain of E-cadherin consists of multiple repeats that are essential for its adhesive function. While the provided references do not directly mention the exact number of extracellular repeats on E-cadherin, it is known that in the classical cadherins, including E-cadherin, there are typically five extracellular cadherin (EC) repeats. Each EC repeat is a domain that is important for mediating homophilic binding interactions between cadherins on adjacent cells, and thus, contributes to cell-cell adhesion.