The gate area contains the conserved DFG (aspartate-phenylalanine-glycine) motif, whose phenylalanine flips in and out of the front pocket, opening and closing a hydrophobic region in the back cleft, i.e., the DFG-in and DFG-out conformation, respectively. The back cleft also comprises the αC-helix with a conserved glutamine residue, which forms a salt bridge with a conserved lysine residue in the gate area. Such a conformation is called αC-in as opposed to αC-out. Researchers have studied kinase similarity between the full -or parts of the -kinome from many different angles. Manning et al. used a multiple sequence alignment (MSA) to cluster the kinome into eight main groups of eukaryotic protein kinases (ACG, CAMK, CK1, CMGC, STE, TK, TKL, and Other) and the atypical protein kinase families. Recently, Modi and Dunbrack 7 assigned some kinases, which were left unassigned in the Other category, based on a structurally validated MSA.