Schematic representation of the primary structure of several members of the ACE protein family. The locations of the active-site zinc-binding motifs are indicated by HEXXH; transmembrane domains are in black. The sequence of gACE is identical to that of the C domain of sACE, except for its first 36 residues. Human gACE and sACE have the same carboxy-terminal transmembrane and cytosolic sequences, whereas ACE2 has a distinct transmembrane and cytosolic sequence. Neither of the Drosophila ACEs, AnCE and Acer, has a membrane-anchoring sequence. Dimensions are not to scale. N, amino terminus; C, carboxyl terminus. The single lines are regions of sequence with no similarity to other proteins. The carboxyl end of ACE2 is homologous to collectin, a non-enzymatic protein associated with renal injury .