What is "ectodomain"

n. (context biochemistry English) The portion of a polypeptide on a cell membrane that extends beyond the membrane into the extracellular space.

An ectodomain is the domain of a membrane protein that extends into the extracellular space (the space outside a cell). Ectodomains are usually the parts of proteins that initiate contact with surfaces, which leads to signal transduction. In SARS-CoV the ectodomain of the spike protein is responsible for attachment to and entry into cells during infection.