A designed repeat protein as an affinity capture reagent

Repeat proteins are an attractive target for protein engineering and design. We have focused our attention on the design and engineering of one particular class: tetratricopeptide repeat (TPR) proteins. In previous work, we have shown that the structure and stability of TPR proteins can be manipulated in a rational fashion [Cortajarena (2011) Prot. Sci. 20, 1042–1047; Main (2003) Structure 11, 497–508]. Building on those studies, we have designed and characterized a number of different peptide-binding TPR modules and we have also assembled these modules into supramolecular arrays [Cortajarena (2009) ACS Chem. Biol. 5, 545—552; Cortajarena (2008) ACS Chem. Biol. 3, 161—166; Jackrel (2009) Prot. Sci. 18, 762—774; Kajander (2007) Acta Crystallogr. D Biol. Crystallogr. 63, 800—811]. Here we focus on the development of one such TPR–peptide interaction for a practical application, affinity purification. We illustrate the general utility of our designed protein interaction. Furthermore, this example highlights how basic research on protein–peptide interactions can lead to the development of novel reagents with important practical applications.