This proposal investigates an enzyme that controls the way a cell is shaped and the way it moves. We have discovered this enzyme called Lfc, which plays a role in a large pathway of information flow that is important in cancer initiation and/or progression. Lfc turns on the molecular switch which is made of another protein called RhoA. When this molecular switch is on, it can stimulate cells to survive under low nutrient conditions and induce cells to grow, change shape and become motile. We employ a methodology called NMR, which enables detection of atoms within the enzyme and its interacting partners. Using this sophisticated methodology, we can monitor the Lfc enzymatic reaction in a real-time under various conditions which mimic cellular environments. We have recently discovered that a molecule called Tctex-1 can bind to Lfc and inhibits the Lfc function. We will endeavor to discover the mechanism underlying this inhibitory effect and hope to characterize the nucleotide exchange activity of Lfc under various physiological conditions including those found in cancer cells.