Anti-K-Ras4A Antibody, Isoform-specific from rabbit, purified by affinity chromatography

GTPase KRas (UniProt P01116; also known as c-K-ras, c-Ki-ras, K-Ras 2, Ki-Ras) is encoded by the KRAS (also known as KRAS2, RASK2) gene (Gene ID 3845) in human. Ras proteins are small GTPases controlling cellular pathways that signal for growth, proliferation, and differentiation. Mammalian genomes harbor three Ras genes (HRAS, NRAS, and KRAS) that encode four GTPases, two of which (K-Ras4A and K-Ras4B) are transcribed from the KRAS gene via two alternative fourth exons. Ras proteins share nearly identical sequence homology in sequence encoded by exons 1-3 (a.a. 1-165), while diverge in their C-terminal 24-a.a. hypervariable region (HVR) encoded by exon 4. The first 165 amino acids form the catalytic G domain that mediates GDP/GTP binding and association with effectors, exchange factors, and GTPase-activating proteins (GAPs), while the C-terminal HVR is needed for Ras membrane localization, a process necessary for Ras function. In addition to the removal of initiator methionine (Met1), Ras proteins are posttranslationally modified by farnesylation of Cys186, followed by proteolytical cleavage their C-terminal end three amino acids (a.a. 187-189) and carboxyl methylation of the newly formed C-terminal prenylcysteine. H-Ras, N-Ras, and K-Ras4A are further palmitoylated on cysteine residue(s) near the C-terminus (Cys181/Cys184 in H-Ras, Cys181 in N- and K-Ras), while K-Ras4B lacks a palmitoylation site. Palmitoylation is required for targeting H- and N-Ras to the plasma membrane (PM), while K-Ras4A and K-Ras4B contain a series of lysines that constitute a polybasic region (PBR) capable of interacting with the inner leaflet of the PM through an electrostatic interaction.