Multiple alignment of sequences. Alignment of AANAT sequences from human (h), ovine (o) and yeast (sc), compared with the newly identified bfAANATs. Sequences have been aligned using CLUSTALW , and then manually adjusted. Residues inversely highlighted in black are identical; residues highlighted in grey are similar among compared sequences. Motifs conserved in vertebrate AANATs and discussed in the text are identified with labeled red boxes. Individual residues discussed in the text are marked with red symbols. Red triangle: conserved lysine; red dots: three residues lacking in all non-vertebrate AANAT homologs; red asterisks: paired histidines involved in catalysis. See Additional file 2 for amphioxus sequence coordinates and Additional file 7 for alignment of AANAT sequences from more species.