EFS Full-Length MS Protein Standard (NP_115835), Labeled with [U- 13C6, 15N4]-L-Arginine and [U- 13C6, 15N2]-L-Lysine, was produced in human 293 cells (HEK293) with fully chemically defined cell culture medium to obtain incorporation efficiency at Creative-Proteomics. The longest protein isoform encoded by this gene contains an SH3 domain, which is known to be important in intracellular signal transduction. The protein encoded by a similiar gene in mice was shown to bind to SH3 domains of protein-tyrosine kinases. The function of this gene is unknown. Three alternatively spliced variants encoding different isoforms have been described for this gene.