The Role of the Interdomain Interactions on RfaH Dynamics and Conformational Transformation

The transcription antiterminator RfaH has been shown to undergo major structural rearrangements to perform multiple functions. Structural determination of the C-terminal domain (CTD) of RfaH showed that it can exist as either an alpha-helix bundle when interfacing with the N-terminal domain (NTD) or as a beta-barrel conformation when it is not interfacing with the NTD. In this paper, we investigate the full RfaH with both CTD and NTD using a variety of all-atom molecular dynamics (MD) simulation techniques, including targeted molecular dynamics, steered molecular dynamics, and adaptive biasing force, and calculate potentials of mean force. We also use network analysis to determine communities of amino acids that are important in transferring information about structural changes. We find that the CTD NTD interdomain interactions constitute the main barrier in the CTD alpha-helix to beta-barrel structural conversion. Once the interfacial interactions are broken, the structural conversion of the CTD is relatively easy. We determined which amino acids play especially important roles in controlling the interdomain motions and also describe subtle structural changes that may be important in the functioning of RfaH.