Avidin

Avidin is a glycoprotein containing four essentially identical subunits, each of which forms an extremely tight complex with biotin. This affinity makes avidin useful in the construction of avidin/biotin-based assay formats. Avidin and biotin are routinely conjugated to indicator enzymes, such as alkaline phosphatase and horseradish peroxidase (HRP), for use in assay development and production.