Differential effects of short affinity tags on the crystallization of Pyrococcus furiosus maltodextrin-binding protein

Pyrococcus furiosus maltodextrin-binding protein readily forms large orthorhombic crystals that diffract to high resolution. This protein was used as a model system to investigate the influence of five short affinity tags (His₆, Arg₅, Strep tag II, FLAG tag and the biotin acceptor peptide) on the formation of protein crystals and their ability to diffract X-­rays. The results indicate that the amino-acid sequence of the tag can have a profound effect on both of these parameters. Consequently, the ability to obtain diffracting crystals of a particular protein may depend as much on which affinity tag is selected as it does on whether an affinity tag is used at all.