Detection of Human Phospho-LKB1/STK11 (S428) by Western Blot. |
Western blot shows lysates of HEK293 human embryonic kidney cell line non-transfected and transfected with human LKB1/STK11 with or without metformin. PVDF membrane was probed with 1 µg/mL Rabbit Anti-Human Phospho-LKB1/STK11 (S428) Antigen Affinity-purified Polyclonal Antibody (Catalog # AF5636) followed by HRP-conjugated Anti-Rabbit IgG Secondary Antibody (Catalog # HAF008). A specific band for Phospho-LKB1/STK11 (S428) was detected at approximately 55 kDa (as indicated). This experiment was conducted under reducing conditions and using Immunoblot Buffer Group 1.
LKB1 (Liver kinase B1; also STK11/Ser/Thr-protein kinase 11 and NY-REN19) is a 55 kDa intracellular member of the LKB1 subfamily, CAMK Ser/Thr protein kinase family of molecules. It is widely expressed, being particularly investigated in small intestinal columnar epithelium and hepatocytes. STK11 is associated with a wide variety of functions, including the initiation of apoptosis through binding to p53, the regulation of TGF-beta signaling through the creation of a SMAD4-LIP1-STK11 complex, and the generation of an epithelial polarized phenotype via cytoskeletal remodeling. Schematically, it would appear that STK11 acts, at least in part, through its ability to phosphorylate multiple AMPK-related kinases, as well as AMPK itself. Human STK11 is 433 amino acids (aa) in length. It potentially contains a three aa propeptide at its C-terminus. The mature segment (aa 1-430) possesses one large protein kinase domain (aa 49-309) plus at least four utilized phosphorylation sites. Phosphorylation on Ser428 promotes the ability of LKB1 to suppress G361 cell growth. Palmitoylation is suggested to occur on Cys418. There are three alternative splice variants. Either individually or in combination, they involve an insertion of nine aa after Tyr126 and a 34 aa substitution for aa 371-433. Full-length human STK11 shares 90% aa sequence identity with mouse STK11. Over the area correspondent to the antigen, human and mouse LKB1 are identical in aa sequence.