Induces cell attachment and spreading and plays a role in cell adhesion (PubMed:10404027). Enhances incorporation of BMP1 in the fibronectin matrix of connective tissues, and subsequent proteolytic activation of lysyl oxidase LOX (PubMed:20181949). Homodimer (By similarity). Interacts with BMP1 and fibronectin (PubMed:20181949). Colocalizes with BMP1 in the Golgi (PubMed:20181949). Preferentially expressed in periosteum and periodontal ligament (PubMed:10404027). Also expressed in the developing and adult heart (PubMed:11335131). In the heart, expressed from embryonic day 10.5. Continues to be strongly expressed throughout cardiac development and into adulthood (PubMed:11335131). By TGF-beta (PubMed:11335131). Gamma-carboxylation is controversial. Gamma-carboxyglutamated; gamma-carboxyglutamate residues are formed by vitamin K dependent carboxylation; these residues may be required for binding to calcium (PubMed:18450759). According to a more recent report in human, does not contain vitamin K-dependent gamma-carboxyglutamate residues (By similarity). Reduced amount of collagen cross-linking in femur and periosteum (PubMed:20181949).