A Disintegrin And Metalloprotease 20 (ADAM20)

ADAM20 and/or ADAM21 is the functional equivalent of sperm fertilin-alpha, since that gene is nonfunctional in human.Sequence analysis of the cDNAs indicated that the 5-prime untranslated region of the ADAM20 mRNA is alternatively spliced.The predicted 726-amino acid ADAM20 protein contains a consensus zinc-binding site of metalloproteases, and both ADAM20 and ADAM21 have putative cell-fusion peptides required for sperm-egg fusion. Overall, the 2 proteins are 50% identical and share sequence similarity with ADAM9 and the fertilins. The exclusive expression of ADAM20 and ADAM21 in human testis and their sequence similarity with the fertilins suggested that they too are expressed on sperm cells and are involved in sperm maturation and/or fertilization.