Purification of Farnesylated hGBP1 and Characterization of Its Polymerization and Membrane Binding

The human guanylate-binding protein 1 (hGBP1) is the best characterized isoform of the seven human GBPs belonging to the superfamily of dynamin-like proteins (DLPs). As known for other DLPs, hGBP1 also exhibits antiviral and antimicrobial activity within the cell. hGBP 1, like hGBPs 2 and 5, carries a CAAX motive at the C-terminus leading to isoprenylation in the living cells. The attachment of a farnesyl anchor and its unique GTPase cycle provides hGBP1 the ability of a nucleotide- stimulated polymerization and membrane binding. In this chapter, we want to show how to prepare farnesylated hGBP1 (hGBP1_fn) by bacterial synthesis and by enzymatic modification, respectively, and how to purify the non-farnesylated, as well as the farnesylated hGBP1, by chromatographic procedures. Furthermore, we want to demonstrate how to investigate the special features of polymerization by a UV-absorption-based turbidity assay and the binding to artificial membranes by means of fluorescence energy transfer.