Development of an affinity pair “Tag-Receptor” for recombinant protein expression and purification

Dissertação apresentada para a obtenção do Grau de Mestre em Biotecnologia, pela Universidade Nova de Lisboa, Faculdade de Ciências e Tecnologia ; The main objective of this work was the development of an affinity pair for the purification of recombinant proteins. In this work, ligands based on the Ugi Reaction and the 1,3,5-Triazine scaffold were synthesised in solid-phase and screened for binding to an affinity tag, an hexapeptide constituted by asparagine aminoacid (N). The ligands were tested against pure solutions of the hexapeptide and Green Fluorescence Protein (GFP), used as a model protein. The ligands that had the highest affinity for the hexapeptide and lowest affinity for the protein were selected for further studies with cellular extracts. The cellular extracts were produced in HEK 293T cells transfected with two designed vectors: one containing the GFP tagged with the affinity tag, and the other containing GFP without tag. The efficient expression of a recombinant GFP fused with the designed affinity tag was demonstrated. The cellular extracts were then loaded onto chromatographic columns containing the lead ligands immobilised onto agarose, and the amount of total protein and GFP bound and eluted noted. The results demonstrated that the Ugi ligands were less selective than the Triazine ligands for the hexapeptide. The triazine ligand 7,4 has been considered as the most selective for the designed affinity tag. In addition, preselected lead ligands for another hexapeptide (RW) of interest were studied. Mammalian cells HEK 293T were transfected with a vector expressing for GFP tagged with this peptide. The ligands immobilized onto agarose were loaded with cellular extracts, being noted that the lead A6C3 showed a high selectivity for the tag tested.