The CILP-1 (cartilage intermediate-layer protein 1) gene product is a 138kD monomeric glycoprotein that is found in both hyaline and fibrocartilage. It is a precursor for two secreted, proteolytically generated products, a 90kD N-terminal CILP-1, and a 62kD C-terminal NTPPHase-homolog. The N-terminus is suggested to serve as both a matrix structural protein, and an IGF-I/TGF-beta1 suppressor sequestration molecule. Human CILP-1 spans aa22-720 of the CILP-1 precursor. It contains one TSP-1 domain (aa149-201) and a C2-type Ig-like region (aa309-395). Over aa1-720 of the CILP-1 precursor, human CILP-1 shares 89% aa identity with mouse CILP-1, and 42% aa identity with human CILP-2.