Detection of Human and Mouse Tmp21/p23 by Western Blot. |
Western blot shows lysates of mouse pancreas tissue, U‑87 MG human glioblastoma/astrocytoma cell line, and human pancreas tissue. PVDF membrane was probed with 0.5 µg/mL of Sheep Anti-Human/Mouse Tmp21/p23 Antigen Affinity-purified Polyclonal Antibody (Catalog # AF7630) followed by HRP-conjugated Anti-Sheep IgG Secondary Antibody (Catalog # HAF016). A specific band was detected for Tmp21/p23 at approximately 21 kDa (as indicated). This experiment was conducted under reducing conditions and using Immunoblot Buffer Group 1.
Tmp21 (Transmembrane protein 21 also TMED-10,Transmembrane emp24 Domain-containing Protein 10, p24δ1 and p23) is a 21‑23 kDa member of the EMP [endosome membrane protein] 24 /GP25L family of cargo molecules. It is ubiquitously expressed, being found associated with the ER-Golgi complex. Molecules destined for secretion are folded/processed in the ER, transported out of the ER via COP-II coated vesicles, united with other molecules in similar vesicles to form an ERGIC/ER-Golgi Intermediate Compartment, and finally delivered to the Golgi (or returned to the ER) via new (presumably COP-I) coated vesicles for terminal maturation. Tmp21 is considered part of both the COP-II and COP-I oligomer complex, the latter that arises from the ERGIC and both stabilizes the ER and allows for the selection of specific molecules targeted for secretion. It also is known to associate with the presenilin complex in the plasma membrane and downregulate gamma ‑secretase activity. This impacts A beta production but not AICD generation. Mature human Tmp21 is a 188 amino acid (aa) type I transmembrane protein. It contains a 154 aa luminal region (aa 32-185) that shows a membrane interaction GOLD (Golgi Dynamics) domain (aa 41-193), and a short 13 aa cytoplasmic tail (aa 207-219) that binds to COP vesicle coat complexes. Exists as both a monomer and homodimer. Over aa 32-185, human Tmp21 shares 97% aa sequence identity with mouse Tmp21.