Human Periostin/OSF-2 Alexa Fluor™ Plus 555-conjugated Antibody

Human OSF-2 (Osteoblast-Specific Factor 2), also known as Periostin, is a 170 kDa secreted homodimeric protein that belongs to the periostin family of the FAS1 superfamily of molecules. It is a TGF-beta inducible molecule that serves as both an adhesion molecule and tumor suppressor. It is synthesized as an 836 amino acid (aa) precursor that contains a 21 aa signal sequence and an 815 aa mature region. It is unknown if the molecule has any significant glycosylation. The human homodimer is not disulfide-linked. The molecule consists of two distinct regions. The N-terminus contains an 55 aa EMI domain, while the C-terminus contains four 130 aa Fasciculin type 1 (FAS1) domains. The EMI domain is cysteine-rich and shows a highly basic alpha-helix. Each FAS1 repeat exhibits a novel seven-stranded beta-wedge with a multiple alpha-helical fold. Three alternate splice forms are known that are C-terminal to the fourfold FAS1 repeats. These mature molecules are 758 and 761 aa in length. The first shows a one aa substitution for aa 649-706 of the mature molecule. The second shows a one aa substitution for aa 649-676, and a deletion of 27 aa between aa 784-810 of the mature molecule. The significance of the alternate splice forms is not clear. OSF-2 is known to bind to alpha_v beta₃ and alpha_v beta₅ integrins. It is synthesized by smooth muscle cells, fibroblasts, osteoblasts, and multiple carcinoma cell types. OSF-2 induces expression of VEGFR2/KDR on endothelial cells (EC) by binding to EC alpha_v beta₃. It also promotes cell transformation to a tumorigenic phenotype, accompanied by MMP-9 and fibronectin production and cell migration. Mature human OSF-2 is 91%, 96% and 91% aa identical to rat, dog, and mouse OSF-2, respectively.