Collectin receptor (C1q receptor): structure and function.

Isolated collectin receptor (C1q receptor) is a single polypeptide chain of approximately 60 kDa (Malhotra and Sim, 1989). Sequence analysis shows that it belongs to a family of proteins which include calreticulin, a component of RoSSA autoantigen, Onchocerca volvulus antigen (RAL-1) and B50 murine melanoma antigen (Malhotra et. al., 1993). The receptor is widely distributed on leukocytes, platelets and endothelium and acts as a receptor for a group of structurally-related complement or lectin opsonins (the collectins), which include C1q, mannose binding protein (MBP), lung surfactant protein A (SP-A) and conglutinin (Malhotra et al., 1990).