Valentin Cepus

Time-Resolved FTIR-Studies of H-Ras P21 GTPase Activity

The small GTP-binding protein H-ras p21 plays a central role in signalling leadi g to cell-growth (1). P21 appears to act as a switch: in the GTP bound form a sig al is given to an effector molecule which is part of a cascade leading to cell proliferation and differentiation. The intrinsic GTPase activity is accelerated by GAP (GTPase activating protein). The transition from the active GTP bound to the inactive GDP bound form is accompanied by a conformational change which has been characterized by time-resolved x-ray structure analysis (2). In order to specify in more detail the structural changes occurring in the GTP to GDP reaction, we have begun complementary investigations by time resolved FTIR difference spectroscopy.