NATURE OF BIOCHEMICAL LESION IN AVIAN RENAL RIBOFLAVINURIA .3. ISOLATION AND CHARACTERIZATION OF RIBOFLAVIN-BINDING PROTEIN FROM EGG ALBUMEN

1. 1. An autosomal recessive strain of white leghorn hens produces eggs with an insufficient supply of riboflavin because of the absence of the riboflavin-binding protein similar to that reported by Rhodes, Bennett and Feeney. This protein has now been isolated from the whites of eggs of homozygous normal hens by a sequence of adsorptions and elutions from DE-32 cellulose on CM-23 cellulose under controlled pH and ionic strength. 2. 2. The protein has a molecular weight of 32 000 by sedimentation equilibrium measurements. 3. 3. The protein contains 14% carbohydrate with glucosamine, galactose and mannose as the component sugars. 4. 4. The protein is highly cross-linked with eight disulfide bridges. No free sulfhydryl groups are present. 5. 5. The amino acid composition is reported. 6. 6. Tryptophan and an acidic group with a pKa of approx. 3.8 have been implicated in the riboflavin-binding. © 1969.