Effect of the alkyl chain modifications of biotinyl derivatives to the binding with streptavidin

Streptavidin (Strep), a homotetrameric 159 residue protein isolated from Streptomices avidinii, binds non-covalently to four molecules of biotin (Bio) with a very high affinity [1]. The Strep-Bio complex provides the basis for many biotechnological applications and is an interesting model system for studying high affinity protein-ligand interactions. The general idea of the approach is that Bio, coupled to low- or high- molecular weight molecules through the lateral chain of pentanoic acid can still be recognised by Strep. In order to increase the versatility and utility of the Strep-Bio system a variety of reagents that can label different functional groups of biologically active compounds have been created [2], For example, the substitution of the pentanoic acid residue with a hydrazide group allows the biotinylation of glycolipids and glycoproteins.