Production and Membrane Binding of N-Terminally Acetylated, C-Terminally Farnesylated and Carboxymethylated KRAS4b.

Recombinant mammalian proteins are routinely produced in E. coli and thus lack post-translational modifications. KRAS4b is processed at both the N- and C-terminus, resulting in an acetylation of the N-terminus (at Thr, after aminopeptidase removal of the original N-term Met) and farnesylation/carboxymethylation of the C-terminal Cys (after proteolytic cleavage of the original C-terminal three amino acids, Val-Iso-Met). Processing of KRAS enables it to associate with the plasma membrane and fulfill its function in cell signaling. We describe here the production of recombinant KRAS4b from our modified baculovirus/insect cell expression system that accurately incorporates these in vivo modifications to allow experiments that anchor KRAS4b to membrane mimetics (e.g., nanodiscs and liposomes).