TMEM189 Full-Length MS Protein Standard (NP_954673), 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 TMEM189-UEV mRNA is an infrequent but naturally occurring read-through transcript of the neighboring TMEM189 and UBE2V1 genes. Ubiquitin-conjugating E2 enzyme variant proteins constitute a distinct subfamily within the E2 protein family. They have sequence similarity to other ubiquitin-conjugating enzymes but lack the conserved cysteine residue that is critical for the catalytic activity of E2s. The protein produced by this transcript has UEV1 B domains but the protein is localized to the cytoplasm rather than to the nucleus. The significance of this read-through mRNA and the function of its protein product has not yet been determined.