New perspectives on the vitamin D binding protein

The serum vitamin D binding protein (DBP), also known as GC‐globulin, is a multifunctional protein known for its role in the transport of vitamin D metabolites. DBP also binds fatty acids and actin monomers, preventing their polymerization that could be detrimental in the circulatory system. DBP may have immune functions independent of its role as a transporter of vitamin D. Because of the abundance of DBP, many aspects of its basic biochemistry were quickly established. Other features of vitamin D action, particularly transcriptional mechanisms of regulation, received greater focus and early interest in DBP centred on its value as a tool for population genetics because of its intriguing genetic variations. Nonetheless, knowledge of DBP mechanisms in physiology was obtained, and functions beyond vitamin D ligand binding were identified. With the recent increased attention regarding the benefits of vitamin D (bone health and immunological regulation), there has been a resurgence of interest in DBP. Because DBP is the primary transporter of vitamin D, it has a role in maintaining the total levels of vitamin D for the organism and in regulating the amounts of free (unbound) vitamin D