Fig. 1.

Schematic representation of the ACE/ACE2 protein family. The active sites (containing the zinc-binding amino acid motif HEMGH) of the N domains in ACE and ACE2 are shown in blue and of the C domains in the somatic and testicular ACE are shown in red. The numbers in the ACE2 extracellular domain correspond to the SARS-CoV-2 binding sites [99]. The ACE2 C-terminal region resembles that of the protein collectrin (shown in pink in both proteins). Collectrin shares no similarity with testicular or somatic ACE. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)