Avidin binding of biotinylated corticotropins

The authors studied the effect on avidin binding of attaching peptide hormones to biotin and biotin analogues. It is concluded that the attachment of ACTH sub(1-24) to biocytin amide and its analogues exerts little influence on the affinity for avidin or succinoylavidin, a result that differs markedly from that obtained with biotinylinsulin-succinoylavidin complexes. The attachment of insulin to biotin weakens significantly the avidin-biotin interaction presumably because the insulin molecular with its stable conformation exerts a steric impediment. Such an effect is not observed with the smaller, flexible biotinylated ACTH sub(1-24) molecules.