Photoregulation of G protein Ras function using photoresponsive protein

The small GTPase Ras functions as a molecular switch in intracellular signaling by cycling between GTP-bound active and GDP-bound inactive states. Here, we developed a photoregulated Ras (PR-Ras) by fusing the photoresponsive protein LOV2-Jα as a photoswitch to its N-terminus. PR-Ras retained intrinsic GTPase activity and reversible photoresponsiveness of LOV2-Jα, with no light-dependent changes in basal GTPase activity. In contrast, clear light-dependent regulation emerged in the presence of regulatory proteins, particularly the Ras-specific guanine nucleotide exchange factor (GEF) under limited GTPase activating protein conditions (GAP). Optimization of GAP concentration enabled visualization of GEF-dependent photocontrol across varying GEF levels. Importantly, disruption of the Ras-GEF allosteric interaction using a GEF mutant abolished light-dependent regulation. These findings demonstrate that PR-Ras photocontrol arises from modulation of regulatory interactions rather than intrinsic catalysis, suggesting that the Ras-GEF allosteric interaction contributes to this regulatory mechanism.