Specificity
Periostin (PN), also designated osteoblast-specific factor 2 (OSF-2), is a disulfide linked protein originally isolated as a osteoblast-specific factor. Periostin is a secreted protein that binds heparin and functions as a ligand for 1). Periostin contains a typical signal sequence, followed by a cysteine-rich domain, a fourfold repeated domain, which shows homology with the insect protein fasciclin, and a C-terminal domain.