Otoraplin/OTOR: Proteins and Enzymes

Otoraplin (OTOR), also known as fibrocyte-derived protein (Fdp) and Melanoma inhibitory activity-like (MIAL), is a secreted 16 kDa globular protein that is preferentially expressed in the inner ear by periotic mesenchyme and developing and mature fibrocytes. It is highly homologous to MIA/cartilage-derived retinoic acid-sensitive protein (CD-RAP), which is a cartilage-specific protein that is also expressed in malignant melanoma cells. The 111 amino acid residue (aa) mature human otoraplin contains one SH3 domain (aa #46-107) and a Tyr at position 50 that is reportedly sulfated. Otoraplin is reported to play a role in the initiation of periotic mesenchyme chondrogenesis. Mature human otoraplin shares 91% and 89% aa sequence identity with dog and mouse otoraplin, respectively.