P122RhoGAP/DLC-1 is a novel dual functional regulator of cell shape and motility and an antioncogenic gene product. Functions of p122RhoGAP/DLC-1 relate not only with cytoskeletal regulation but also subtle tuning of Ca2+ / phosphoinositide signaling. These are based on the intramolecular structure, especially domain structure of the molecule. I aim to explore the functional characterization of the START domain, a candidate domain for lipid binding and / or transfer , of p122RhoGAP/DLC-1. The process of tumor progression is still poorly understood. Mechanism for regulation of cell proliferation,cell motility and invasiveness are important for the development of cancer and potential target for cancer therapy. P122RhoGAP/DLC-1 has some functional domains such as RhoGTPase activating protein domain, which has been hypothesized to be the basis of its tumor suppressive actions and a steroidigenic acute regulatory(StAR) related lipid transfer START domain, both located in its C-terminal domain. The lipid binding function is still unknown in the case of p122RhoGAP/DLC-1.