A RhoA structure with switch II flipped outward revealed the conformational dynamics of switch II region

Small GTPase RhoA switches from GTP-bound state to GDP-bound state by hydrolyzing GTP, which is acceler-ated by GTPases activating proteins (GAPs). However, less study of RhoA structural dynamic changes was conducted during this process, which is essential for understanding the molecular mechanism of GAP dissocia-tion. Here, we solved a RhoA structure in GDP-bound state with switch II flipped outward. Because lacking the intermolecular interactions with guanine nucleotide, we proposed this conformation of RhoA could be an in-termediate after GAP dissociation. Further molecular dynamics simulations found the conformational changes of switch regions are indeed existing in RhoA and involved in the regulation of GAP dissociation and GEF recog-nition. Besides, the guanine nucleotide binding pocket extended to switch II region, indicating a potential druggable cavity for RhoA. Taken together, our study provides a deeper understanding of the dynamic properties of RhoA switch regions and highlights the direction for future drug development.

Automated summary

RhoA, a small GTPase, undergoes a conformational change from a GTP-bound state to a GDP-bound state through GTP hydrolysis, which is accelerated by GTPases activating proteins (GAPs). However, the dynamic changes in RhoA's structure during this process have been less studied, despite their importance in understanding GAP dissociation. In this study, we determined the structure of RhoA in the GDP-bound state with an outward-flipped switch II, suggesting this conformation could be an intermediate after GAP dissociation. Molecular dynamics simulations further revealed that the conformational changes in the switch regions indeed occur in RhoA and are involved in GAP dissociation and GEF recognition. Additionally, the guanine nucleotide binding pocket extends to the switch II region, providing a potential druggable cavity for RhoA. Overall, our study enhances the understanding of the dynamic properties of RhoA's switch regions and highlights their potential in future drug development.