Final answer:
Connexin is the protein found in gap junctions that allows for cell-cell communication, crucial for processes like heart muscle contraction.
Step-by-step explanation:
The protein found in gap junctions that provides cell-cell communication is Connexin. Gap junctions facilitate the direct movement of ions and small molecules between cells, allowing for rapid communication that is essential in coordinating activities such as cardiac muscle contraction, where cells need to contract in unison. These junctions develop when a set of six connexin proteins in the plasma membrane arrange themselves into a connexon, forming a channel between adjacent animal cells.