ADAM20

Disintegrin and metalloproteinase domain-containing protein 20 is an enzyme encoded by the ADAM20 gene in humans. It is a membrane disintegrin-metalloprotease that belongs to the ADAM family. It is exclusively expressed in the Testes and is similar to sperm cell-specific fertilins -alpha and -beta.
Its cDNA is tightly linked to marker SHGC-36001 on chromosome 14q24.1. ADAM20 is related to fertilin α, fertilin β, and fertilin γ. In humans, fertilin α has recently been deactivated so that ADAM20 may be the functional equivalent of fertilin α in humans.

Structure

In common with other ADAM family members, ADAM20 contains a N-terminal reprolysin family propeptide, reprolysin family zinc metalloprotease domain, disintegrin domain, and a C-terminal ADAM cysteine-rich domain.
The propeptide acts as a signal peptide and an activator domain. This prodomain has a cysteine that interacts with a zinc in the catalytic domain, thereby preventing the catalytic activity of the protein. When the pro-protein domain is cleaved, this cysteine zinc bond is broken, and the protein is activated. A notable variant showed an amino acid difference in the pro protein domain that prevented the cleavage of this domain, which prevented the fusion of the sperm cell to an egg.