Fig. 2: Identification of the proton channel in TolQ.
From: Deciphering the molecular mechanism of the bacterial division motor TolQRA
a The interactive interface between the transmembrane helix of TolR dimer, showing a leucine-rich motif (L21LDVLLVLLL30). The side chains of amino acids L21–L30 are depicted, and the interactions are highlighted. b Top view of the TolQR structure, showing the channel cavity. The interactions between the putative proton acceptor D23 of TolR and the conserved T145 and T178 of TolQ are highlighted (right boxed panel). The side chain of D23 on TolR chain B is oriented towards TolQ5 (blue), forming hydrogen bonds with TolQ_T145 and TolQ_T178. The side chain of D23 on TolR chain A is oriented towards TolQ2 (yellow) and TolQ3 (orange) and shows no interaction with the conserved threonines T145 and T178 (right boxed panel). c Cell viability of mutants with substitutions in the TolR N-terminus and the putative proton channel of TolQ. d MD simulations reveal the formation of a water channel between TM2 and TM3 of the TolQ subunit 3, with channel-related side chains depicted. Simulations of water entry into the channel under different protonation states are shown (D23, being deprotonated, hydrated, and protonated states from left to right).
