Embryonal Fyn Associated Substrate (EFS)

By screening a hippocampus cDNA library with mouse Efs, Ishino et al. (1997) cloned 2 splice variants of human EFS. The longer transcript has 2 polyadenylation signals and encodes a deduced 561-amino acid protein containing an N-terminal SH3 domain, 5 central YxxP motifs, and a proline-rich region in its C-terminal half. The shorter transcript encodes a 468-amino acid protein that lacks the SH3 domain.

The SH3 domains of mouse and human EFS are identical, but the rest of the proteins share only 78% identity. Northern blot analysis detected both variants in all mouse tissues examined. Western blot analysis of human tissue lysates detected a major 90-kD band and several bands of 67 to 70 kD that represent proteins lacking the SH3 domain.