STK3, also known as serine/threonine-protein kinase 3, is a mammalian Ste20-related protein kinases most closely related to Drosophila Hippo, a major regulator of cell proliferation and survival during development. It is a serine/threonine kinase that functions early in a pheromone responsive signal transduction cascade in yeast. It activates the human large tumor suppressor kinase Lats1. It modulates stress-induced cardiac hypertrophy. Recombinant human STK3, fused to His-tag at C-terminus, was expressed in insect cell and purified by using conventional chromatography techniques.