Vitamin D-binding protein

Vitamin D-binding protein, also known as gc-globulin (group-specific component), is a is_associated_with::protein that in humans is encoded by the GC is_associated_with::gene.

Function
Vitamin D-binding protein belongs to the is_associated_with::albumin gene family, together with is_associated_with::human serum albumin and is_associated_with::alpha-fetoprotein. It is a multifunctional protein found in plasma, is_associated_with::ascitic fluid, is_associated_with::cerebrospinal fluid and on the surface of many cell types. It binds to is_associated_with::vitamin D and its plasma metabolites and transports them to target tissues. As Gc protein-derived macrophage activating factor it is a Macrophage Activating Factor (MAF) that has been tested for use as a cancer treatment that would activate is_associated_with::macrophages against cancer cells.

Structure
Human GC is a glycosylated alpha-globulin, ~58 kDa in size. Its 458 amino acids are coded for by 1690 nucleotides on chromosome 4 (4q11–q13). The primary structure contains 28 cysteine residues forming multiple disulfide bonds. GC contains 3 domains. Domain 1 is composed of 10 alpha helices, domain 2 of 9, and domain 3 of 4.