FGF-R1, fibroblast growth factor receptor 1, also known as CD331, is a receptor tyrosine kinase whose ligand is a specific member of the fibroblast growth factor family. FGF-R1 is a full-length representative protein, which consists of an extracellular domain, three immunoglobulin-like domains, a hydrophobic transmembrane fragment and a cytoplasmic tyrosine kinase domain. The extracellular domain of FGF-R1 interacts with specific extracellular fibroblast growth factors, initiating a series of downstream signals and affecting cell mitosis and differentiation. FGF-R1 protein is considered to play an important role in the development of nervous system. The protein may also help regulate the growth of long bones, such as large bones in the arms and legs.