The three RAF proteins, ARAF, BRAF and CRAF each share three conserved regions; CR1, CR2 and CR3. CR1 is essential for binding to RAS at the plasma membrane, CR2 contains a binding site for 14-3-3 protein, and CR3 is the kinase domain and includes the phosphorylation loop (P-loop), activation loop (A-loop) and is responsible for RAF dimerisation and phosphorylation of MEK1/2. The glycine rich P-loop is important for binding ATP. Phosphorylation of the threonine and serine residues within the activation loop is essential for the kinase function of each RAF protein. Adjacent to CR3 is the N-terminal acidic region (NtA). Two residues of the NtA need to be phosphorylated for ARAF (S299, Y301, Y302) and CRAF (S338, S339, Y340, Y341) to dimerise, whereas BRAF is constitutively phosphorylated at the serine residues (S445, S446) and has an aspartic acid residue instead of a tyrosine (D447, D448) to impart a constitutive negative charge. This region interacts with the aC-helix to form the RAF dimerisation interface. The C-terminus of each RAF protein contains a second binding site for 14-3-3 proteins. BRAF and CRAF each contain several ERK phosphorylation sites that form part of negative loops to reduce RAF activity. Several of these feedback sites are conserved between RAF species. Loci for BRAF mutations are also shown, with class I BRAF mutations occurring within the activation loop at V600, class II mutations frequently occurring at G469 in the P-loop, and class III mutations frequently occurring at G466 in the P-loop. Finally, a sequence alignment of the NtA sequence of the ARAF, BRAF, CRAF, KSR1 and KSR2 is shown. The serine and tyrosine residues in ARAF and CRAF are able to be phosphorylated, with the serine residues of BRAF being constitutively phosphorylated. The NtA region in KSR1 contains a tyrosine residue which can be phosphorylated and may play a role in activating BRAF.