SPARC Related Modular Calcium Binding Protein 1 (SMOC1)

The mature 408-amino acid protein contains a 26-residue signal peptide at the N terminus, followed by a follistatin-like domain, 2 thyroglobulin-like domains interrupted by a novel domain, and an extracellular calcium-binding domain. Recombinant expression in human cells showed that SMOC1 is a glycoprotein with a calcium-dependent conformation. Circular dichroism spectroscopy showed that SMOC1 has an approximately 40% beta-sheet structure. Northern blot analysis of adult mouse tissues revealed a 3.7-kb transcript with strong expression in ovary, and lower expression in brain, thymus, heart, skeletal muscle, liver, and lung. RT-PCR analysis detected a signal in testis also. Immunofluorescence studies showed that SMOC1 localized to basement membranes both in cultured cells and in mouse skin, kidney, and ovary.