Identification and molecular characterization of a biotin-binding protein distinct from avidin of chicken egg white and comparison with yolk biotin-binding protein

By immunol. and biochem. methods a biotin-binding protein, distinct from avidin, was shown to be present in chicken egg white. This vitamin-binding protein (mol. wt. 67,000) bound [14C]biotin, displayed thermally induced biotin exchange reaction, and exhibited gross immunol. cross-reactivity with the purified yolk biotin-binding protein. In vitro labeling of sol. proteins with radioactive amino acids in the oviduct tissue explants from estrogenized chicks revealed that .apprx.2% of the total radioactive proteins immunopptd. with anti-yolk biotin-binding protein antibodies. The protein was purified to homogeneity by ion-exchange chromatog. on DEAE-cellulose and biotin-AH Sepharose affinity chromatog. The purified protein specifically bound [14C]biotin, and exhibited complete immunol. homol. with the yolk biotin-binding protein but not with avidin. Its electrophoretic mobility (at pH 8.3), acidic nature, biotin-binding characteristics, immunol. cross-reactivity, and tryptic peptide maps were very similar to those of yolk biotin-binding protein, and not avidin