Human LKB1 Synthetic Peptide. LKB1 (also known as STK11 - Serine/threonine-protein kinase STK11), a member of the serine/threonine kinase family, is a tumor suppressor. LKB1 physically associates with p53 and regulates specific p53 dependent apoptosis pathways. LKB1 is present in both the cytoplasm and nucleus of living cells and translocates to mitochondria during apoptosis. LKB1 functions as a master upstream protein kinase, regulating AMPK related kinases as well as AMPK. Mutations in LKB1 gene are associated with Peutz Jeghers syndrome.