Foods with a relatively high biotin content include Swiss chard, raw egg yolk (however, the consumption of avidin-containing egg whites with egg yolks minimizes the effectiveness of egg yolk's biotin in one's body), liver, Saskatoon berries, and leafy green vegetables.
The different sub-units may have each their own activity, such as binding biotin in avidin tetramers, or have a common biological property, such as the allosteric binding of oxygen in hemoglobin.