This domain is found in the extracellular portion of receptor-like proteins - such as serine/threonine kinases and adenylyl cyclases. This is a ligand-binding domain that binds cytokinin (Matilla et.al., FEMS Microbiology Reviews, fuab043, 45, 2021, 1. https://doi.org/10.1093/femsre/fuab043).
Jiyao W et al.(2023). "The conserved domain database in 2023.",