Avidin binding of carboxyl-substituted biotin and analogs

The use of biotinylated hormones as ligands on avidin-Sepharose columns represents an attractive approach to the isolation of receptors. However, the strong noncovalent interaction between the hormone and its receptor on one hand and biotin and avidin on the other poses major obstacles to receptor retrieval. The authors report the results of a systematic search for weaker binding biotin containing ligands that are displaceable by biotin. The experiments indicate that the attachment of insulin to biotin or biotin analogues imposes a steric impediment to the interaction of the biotin residues with their avidin or succinoylavidin binding sites. The observation that insertion of a spacer between the avidin binding site and the insulin molecule increases the stability of the complexes supports this view.