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Catalytic domain of the Serine/Threonine kinase, Liver Kinase B1 STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. LKB1, also called STK11, was first identified as a tumor suppressor responsible for Peutz-Jeghers syndrome, a disorder that leads to an increased risk of spontaneous epithelial cancer. It serves as a master upstream kinase that activates AMP-activated protein kinase (AMPK) and most AMPK-like kinases. LKB1 and AMPK are part of an energy-sensing pathway that links cell energy to metabolism and cell growth. They play critical roles in the establishment and maintenance of cell polarity, cell proliferation, cytoskeletal organization, as well as T-cell metabolism, including T-cell development, homeostasis, and effector function. To be activated, LKB1 requires the adaptor proteins STe20-Related ADaptor (STRAD) and mouse protein 25 (MO25). The LKB1 subfamily is part of a larger superfamily that includes the catalytic domains of other STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.
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