title: Purification of biotin-binding protein from chicken egg yolk and comparison with avidin.
abstract: A simple alternative procedure for the purification in higher yields of the biotin-binding protein from the chicken egg yolk in a ligand-free form is described. The isolated protein was homogeneous by the criteria of polyacrylamide gel electrophoresis, gel filtration chromatography, immuno-double diffusion and immuno-electrophoresis. The protein had an Mr of 72 000 +/- 2000 and was a homotetramer of subunit Mr of 18 000 +/- 1000. It bound [14C]biotin in the molar ratio of 1:4 with an association constant (Ka) of 0.58 X 10(12) M-1. The yolk biotin-binding protein and avidin exhibited qualitatively similar spectral changes on interaction with biotin and p- hydroxyazobenzoic acid, but quantitatively these changes were more pronounced with avidin. Despite the lack of gross immunological cross-reactivity between the two biotin-binders, evidence based on immunological techniques for some degree of common conformational characteristics restricted to or around the ligand-binding sites of the two proteins was adduced. The mixed subunits of the two proteins failed to form hetero-oligomers on reconstitution.
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology; D001360:Avidin / Q000032:analysis* / Q000276:immunology; D001391:Azo Compounds / Q000378:metabolism; D001710:Biotin / Q000378:metabolism; D002352:Carrier Proteins / Q000276:immunology / Q000302:isolation & purification*; D002645:Chickens; D004530:Egg Yolk / Q000032:analysis*; D005260:Female; D007700:Kinetics; D008970:Molecular Weight; D010047:Ovalbumin / Q000031:analogs & derivatives*; D013053:Spectrophotometry; D013696:Temperature
chemical_list: D000906:Antibodies; D001391:Azo Compounds; D002352:Carrier Proteins; C017071:biotin-binding proteins; D001360:Avidin; D001710:Biotin; D010047:Ovalbumin