Hybrid Exb/Mot stators require substitutions distant from the chimeric pore to power flagellar rotation

Ion-powered rotary motors (IRMs) underpin the rotation of one of nature's oldest wheels, the flagellar motor. Recent structures show that this complex appears to be a fundamental molecular module with diverse biological utility where electrical energy is coupled to torque. Here, we attempted to rationally design chimeric IRMs to explore the cross-compatibility of these ancient motors. We succeeded in making one working chimera of a flagellar motor and a non-flagellar transport system protein. This had only a short hybrid stretch in the ion-conducting channel, and function was subsequently improved through additional substitutions at sites distant from this hybrid pore region. Our goal was to test the cross-compatibility of these homologous systems and highlight challenges arising when engineering new rotary motors.