Enables transforming growth factor beta receptor binding activity. Acts upstream of or within several processes, including brown fat cell differentiation; positive regulation of endothelial cell proliferation; and positive regulation of transforming growth factor beta receptor signaling pathway. Located in extracellular space. Is expressed in pancreas mesenchyme. Orthologous to human LRG1 (leucine rich alpha-2-glycoprotein 1). [provided by Alliance of Genome Resources, Apr 2022]