MED21 Full-Length MS Protein Standard (NP_004255), 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. This gene encodes a member of the mediator complex subunit 21 family. The encoded protein interacts with the human RNA polymerase II holoenzyme and is involved in transcriptional regulation of RNA polymerase II transcribed genes. A pseudogene of this gene is located on chromosome 8. Alternative splicing results in multiple transcript variants.