Enables LBD domain binding activity. Acts upstream of or within positive regulation of protein binding activity; positive regulation of protein processing; and regulation of amyloid precursor protein catabolic process. Located in collagen-containing extracellular matrix. Is expressed in aorta; jaw bone; nervous system; and sensory organ. Orthologous to human SPON1 (spondin 1). [provided by Alliance of Genome Resources, Apr 2022]