Recombinant human KRAS (KRAS proto-oncogene GTPase), isoform a, encompassing amino acids 2-186(end). This construct contains an N-terminal His-tag (6xHis) followed by an optimal TEV protease target sequence that allows cleavage of the His-tag from the protein (TEV: tobacco etch virus cysteine protease BPS Bioscience #50308). The protein also contains mutation of interest G12D. The protein was affinity purified and loaded with GppNHp, a non-hydrolyzable GTP analog. Unbound GppNHp was removed by spin column. Ready for use in KRAS-RAF binding studies or inhibitor assays.