AVIDIN. 2. PURIFICATION AND COMPOSITION

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Abstract
A simple large-scale purification of avidin from fresh egg white by gradient elution from carboxy-methylcellulose has been devised. Two or three active components of similar biotin-binding activity were shown to be present. Two of these were separated on columns of Amberlite CG-50, and found to differ slightly in their amino acid composition, suggesting that the differences may be genetic in origin. The most active preparations bound 13.8 ug. of biotin/mg. of avidin, corresponding to an equivalent weight of 17,700. This shows that each molecule of avidin can bind three molecules of biotin. The composition of avidin was completely accounted for in terms of amino acid and carbohydrate residues.