The major results of the present work are related to low molecular weight guanosine triphosphate (GTP) binding Ras proteins which play an essential role in a variety of diverse cellular signal transduction and transport processes by cycling between a GTP-bound �on� state and a guanosine diphosphate (GDP) bound �off� state. Ras(wt)·Mg2+·GppNHp exists in two biological relevant conformational states: state 1 and state 2. State 1 is an "open", disordered conformation of the switch regions similar to the GDP-bound state. State 2 appears to be very similar to the conformation of Ras in the "on" state which is observed for Ras interacting with effector proteins. It was shown that the wild-type protein molecules preferentially exist in state 2. Mutant protein molecules preferentially exist in the "open" state 1.