Abstract: The present invention relates to an isolated BMP receptor kinase protein or soluble fragment thereof, a DNA sequence coding for said BMP receptor kinase protein or said soluble fragment thereof, a recombinant expression vector comprising said DNA sequence, a host cell comprising said recombinant expression vector, a method of expressing said BMP receptor kinase protein or soluble fragment thereof, a method for identifying compounds capable of binding to said BMP receptor kinase protein or soluble fragment thereof, a method for determining the amount of such compounds in a sample, and antibodies to said BMP receptor kinase protein.