Activin A receptor type II-like 1 (ACVRL1) is a type I cell-surface receptor for the TGF-beta superfamily of ligands. ACVRL1, similar to other type 1 receptors, has a conserved serine-threonine kinase subdomain, a glycine- and serine-rich region (called the GS domain) preceding the kinase domain, and a short C-terminal tail. Mutations in ACVRL1 are associated with hemorrhagic telangiectasia type 2.