Activity sites of angiotensin-converting enzyme.

(a) Organization of the ACE protein. The active sites, located in α13 and α14 of ACE, are indicated by a black rectangle. (b) Zinc-binding motif. The residues that surround the Zn2+are represented by pink sticks. (c) The hydrogen bond interaction between Zn2+ and key residues. The distance between key residues and zinc is shown by aligplot.