EF-hand, extracellular calcium-binding (EC) motif, found in secreted modular calcium-binding protein 2 (SMOC-2)
SMOC-2, also termed SPARC-related modular calcium-binding protein 2, or smooth muscle-associated protein 2 (SMAP-2), is a ubiquitously expressed matricellular protein that enhances the response to angiogenic growth factors, mediate cell adhesion, keratinocyte migration, and metastasis. It is also associated with vitiligo and craniofacial and dental defects. Moreover, SMOC-2 acts as an Arf1 GTPase-activating protein (GAP) that interacts with clathrin heavy chain (CHC) and clathrin assembly protein CALM and functions in the retrograde, early endosome/trans-Golgi network (TGN) pathway in a clathrin- and AP-1-dependent manner. It also contributes to mitogenesis via activation of integrin-linked kinase (ILK). SMOC-2 contains a follistatin-like (FS) domain, two thyroglobulin-like (TY) domains, a novel domain, which is found only in the homologous SMOC-1, and an extracellular calcium-binding (EC) domain with two EF-hand calcium-binding motifs.